Filed Pursuant to Rule 424(b)(5)
Registration No. 333-254906

P R O S P E C T U S   S U P P L E M E N T

(To Prospectus Dated March 31, 2021)

ATI Inc.

$425,000,000

7.250% Senior Notes due 2030

We are offering $425,000,000 aggregate principal amount of our 7.250% Senior Notes due 2030 (the “notes”). The notes will mature on August 15, 2030. Interest will accrue from August 11, 2023, and the first interest payment date will be February 15, 2024.

We may redeem the notes in whole or in part at any time at the applicable redemption prices set forth under “Description of Notes — Optional Redemption.” We must offer to repurchase the notes upon the occurrence of a change of control triggering event at the price described in this prospectus supplement in “Description of Notes — Purchase of Notes upon a Change of Control Repurchase Event.”

The notes will be our senior unsecured obligations, ranking equally in right of payment with all of our existing and future senior unsecured indebtedness and senior to our future subordinated indebtedness. The notes will be effectively subordinated to our existing and future secured indebtedness to the extent of the value of the assets securing that indebtedness and to the existing and future indebtedness and other liabilities of our subsidiaries. We conduct a significant portion of our business through our subsidiaries. None of our subsidiaries will guarantee the notes.

You should read this prospectus supplement and the accompanying prospectus carefully before you invest in our notes. Investing in our notes involves a high degree of risk. See “Risk Factors” beginning on page S-15 for a discussion of certain risks that you should consider in connection with an investment in the notes.

Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of these notes or passed upon the adequacy or accuracy of this prospectus supplement or the accompanying prospectus. Any representation to the contrary is a criminal offense.

	Price to Public			Underwriting Discounts			Proceeds to ATI (before expenses)(1)
Per note		100.000	%		1.125	%		98.875	%
Total	$	425,000,000		$	4,781,250		$	420,218,750

(1) Plus accrued interest, if any, from August 11, 2023.

The notes will not be listed on any securities exchange or automated quotation system.

We expect that delivery of the notes will be made to investors in book-entry form through The Depository Trust Company for the accounts of its participants, including Clearstream Banking, société anonyme, and Euroclear Banking, S.A./N.V., on or about August 11, 2023.

Book-Running Managers

Citigroup Goldman Sachs & Co. LLC J.P. Morgan

Co-Managers

BofA Securities PNC Capital Markets LLC

MUFG Wells Fargo Securities HSBC

The date of this prospectus supplement is August 7, 2023.

TABLE OF CONTENTS

Prospectus Supplement

	Page
About This Prospectus Supplement		S-ii
Where You Can Find More Information		S-iii
Forward Looking Statements		S-v
Summary		S-1
Risk Factors		S-15
Use of Proceeds		S-21
Capitalization		S-22
Description of Notes		S-23
Material U.S. Federal Income Tax Considerations		S-41
Underwriting		S-47
Legal Matters		S-51
Experts		S-51

Prospectus
About this Prospectus	i
Where You Can Find More Information	ii
Summary	1
Risk Factors	1
Forward-Looking Statements	1
Use of Proceeds	2
Description of Debt Securities	3
Description of Other Securities	22
Description of Capital Stock	23
Plan of Distribution	28
Legal Matters	30
Experts	30

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ABOUT THIS PROSPECTUS SUPPLEMENT

This document is in two parts. The first part is this prospectus supplement, which describes certain matters relating to us and this offering. The second part, the accompanying prospectus dated March 31, 2021, gives more general information about securities, including debt securities, we may offer from time to time, some of which may not apply to the notes offered by this prospectus supplement and the accompanying prospectus. For information about the notes, see “Description of Notes” in this prospectus supplement and “Description of Debt Securities” in the accompanying prospectus.

We are responsible for the information contained and incorporated by reference in this prospectus supplement and the accompanying prospectus and in any related free-writing prospectus we prepare or authorize. We have not authorized anyone to give you any other information, and we take no responsibility for any other information that others may give you. We are not, and the underwriters are not, making an offer of these notes in any jurisdiction where the offer or sale is not permitted. You should not assume that the information contained in this prospectus supplement, the accompanying prospectus or the documents incorporated by reference in this prospectus supplement or the accompanying prospectus is accurate as of any date other than their respective dates. Our business, financial condition, results of operations and prospects may have changed since those dates.

Before you invest in the notes, you should carefully read this prospectus supplement and the accompanying prospectus. You should also read the documents we have referred you to under “Where You Can Find More Information” for information about us. The shelf registration statement described in the accompanying prospectus, including the exhibits thereto, can be read at the Securities and Exchange Commission’s (the “SEC”) website as described under “Where You Can Find More Information.”

If the information set forth in this prospectus supplement varies in any way from the information set forth in the accompanying prospectus, you should rely on the information contained in this prospectus supplement. If the information set forth in this prospectus supplement varies in any way from the information set forth in a document we have incorporated by reference, you should rely on the information in the more recent document.

Unless indicated otherwise, or the context otherwise requires, references in this document to “ATI,” “the Company,” “we,” “us” and “our” are to ATI Inc. and its consolidated subsidiaries, and references to “dollars” and “$” are to United States dollars.

This prospectus supplement and accompanying prospectus include registered trademarks, trade names and service marks of the Company and its subsidiaries.

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WHERE YOU CAN FIND MORE INFORMATION

Available Information

We file reports, proxy statements and other information with the SEC. The SEC maintains a website that contains reports, proxy and information statements and other information regarding issuers that file electronically with the SEC, including us. The SEC’s website is http://www.sec.gov. Our website is http://www.ATImaterials.com. Information contained on or accessible through our website is not part of, and should not be construed as being incorporated by reference into, this prospectus supplement and the accompanying prospectus.

Incorporation by Reference

The SEC allows us to “incorporate by reference” information that we file with it. This means that we can disclose important information to you by referring you to other documents. Any information we incorporate in this manner is considered part of this prospectus supplement and the accompanying prospectus except to the extent updated and superseded by information contained in this prospectus supplement and the accompanying prospectus. Some information that we file with the SEC after the date of this prospectus supplement and until we sell all of the securities covered by this prospectus supplement will automatically update and supersede the information contained in this prospectus supplement and the accompanying prospectus.

We incorporate by reference the following documents that we have filed with the SEC and any filings that we make with the SEC in the future under Sections 13(a), 13(c), 14 or 15(d) of the Securities Exchange Act of 1934, as amended (the “Exchange Act”), until we sell all of the securities covered by this prospectus supplement, including between the date of this prospectus supplement and the date on which the offering of the securities under this prospectus supplement is terminated, except as noted in the paragraph below:

Our SEC Filings (File No. 1-12001)	Period for or Date of Filing
Annual Report on Form 10-K	Year Ended December 31, 2022
Quarterly Reports on Form 10-Q	Quarters Ended March  31 and June 30, 2023
Current Reports on Form 8-K	March  2, May  4, May  15, June 6  and August 7, 2023

Pursuant to General Instruction B of Form 8-K, any information submitted under Item 2.02, Results of Operations and Financial Condition, or Item 7.01, Regulation FD Disclosure, of Form 8-K is not deemed to be “filed” for the purpose of Section 18 of the Exchange Act, and we are not subject to the liabilities of Section 18 with respect to information deemed furnished (and not filed) in accordance with SEC rules, including information submitted under Item 2.02 or Item 7.01 of Form 8-K. We are not incorporating by reference any information deemed furnished (and not filed) in accordance with SEC rules, including information submitted under Item 2.02 or Item 7.01 of Form 8-K, into any filing under the Securities Act of 1933, as amended (the “Securities Act”), or the Exchange Act or into this prospectus supplement or the accompanying prospectus.

Statements contained in this prospectus supplement or the accompanying prospectus as to the contents of any contract, agreement or other document referred to in this prospectus supplement or the accompanying prospectus do not purport to be complete, and where reference is made to the particular provisions of that contract, agreement or other document, those references are qualified in all respects by reference to all of the provisions contained in that contract or other document. For a more complete understanding and description of each such contract, agreement or other document, we urge you to read the documents contained in the exhibits to the registration statement of which the accompanying prospectus is a part.

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Any statement contained in a document incorporated by reference, or deemed to be incorporated by reference, into this prospectus supplement and the accompanying prospectus will be deemed to be modified or superseded for purposes of this prospectus supplement and the accompanying prospectus to the extent that a statement contained herein, therein or in any other subsequently filed document which also is incorporated by reference in this prospectus supplement and the accompanying prospectus modifies or supersedes that statement. Any such statement so modified or superseded will not be deemed, except as so modified or superseded, to constitute a part of this prospectus supplement and the accompanying prospectus.

We will provide without charge, upon written or oral request, a copy of any or all of the documents that are incorporated by reference into this prospectus supplement and the accompanying prospectus and a copy of any or all other contracts, agreements or documents which are referred to in this prospectus supplement or the accompanying prospectus. Requests should be directed to: ATI Inc., 116 15^th Street, Suite 301, Pittsburgh, PA 15222, Attention: Corporate Secretary; telephone number: (800) 289-7454. You also may review a copy of the registration statement of which the accompanying prospectus is a part and its exhibits through the SEC’s website.

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FORWARD-LOOKING STATEMENTS

You should carefully review the information contained in or incorporated by reference into this prospectus supplement and the accompanying prospectus. In this prospectus supplement and the accompanying prospectus, statements that are not reported financial results or other historical information are “forward-looking statements.” Forward-looking statements give current expectations or forecasts of future events and are not guarantees of future performance. They are based on our management’s expectations that involve a number of business risks and uncertainties, any of which could cause actual results to differ materially from those expressed in or implied by the forward-looking statements.

You can identify these forward-looking statements by the fact that they do not relate strictly to historic or current facts. They use words such as “anticipates,” “believes,” “estimates,” “expects,” “would,” “should,” “will,” “will likely result,” “forecast,” “outlook,” “projects,” and similar expressions in connection with any discussion of future operating or financial performance.

We cannot guarantee that any forward-looking statements will be realized, although we believe that we have been prudent in our plans and assumptions. Achievement of future results is subject to risks, uncertainties and assumptions that may prove to be inaccurate. Among others, the factors discussed in the “Risk Factors” section of our Annual Report on Form 10-K for our fiscal year ended December 31, 2022, or under “Risk Factors” in this prospectus supplement could cause actual results to differ from those in forward-looking statements included in or incorporated by reference into this prospectus supplement and the accompanying prospectus or that we otherwise make. Important factors that could cause actual results to differ materially from those in the forward-looking statements include: (a) material adverse changes in economic or industry conditions generally, including global supply and demand conditions and prices for our specialty materials and changes in international trade duties and other aspects of international trade policy; (b) material adverse changes in the markets we serve; (c) our inability to achieve the level of cost savings, productivity improvements, synergies, growth or other benefits anticipated by management, from strategic investments and the integration of acquired businesses; (d) volatility in the price and availability of the raw materials that are critical to the manufacture of our products; (e) declines in the value of our defined benefit pension plan assets or unfavorable changes in laws or regulations that govern pension plan funding; (f) labor disputes or work stoppages; (g) equipment outages; (h) business and economic disruptions associated with extraordinary events beyond our control, such as war, terrorism, international conflicts, public health issues such as health epidemics or pandemics, natural disasters and climate-related events; and (i) other risk factors summarized in our Annual Report on Form 10-K for the year ended December 31, 2022, and in other reports filed with the SEC. Should known or unknown risks or uncertainties materialize, or should underlying assumptions prove to be inaccurate, actual results could vary materially from those anticipated, estimated or projected. You should bear this in mind as you consider any forward-looking statements.

We undertake no obligation to publicly update forward-looking statements, whether as a result of new information, future events or otherwise, except as may be required by law. You are advised, however, to consider any additional disclosures that we may make on related subjects in future filings with the SEC. You should understand that it is not possible to predict or identify all factors that could cause our actual results to differ. Consequently, you should not consider any list of factors to be a complete set of all potential risks or uncertainties.

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SUMMARY

This summary highlights selected information contained elsewhere in this prospectus supplement, the accompanying prospectus and the documents incorporated by reference in this prospectus supplement. Because the following is only a summary, it does not contain all of the information that may be important to you. You should carefully read this prospectus supplement, the accompanying prospectus and the documents incorporated by reference before deciding whether to invest in the notes.

Our Company

We are a global manufacturer of technically advanced specialty materials and complex components. Our largest markets are aerospace & defense, representing approximately 57% of sales for the six months ended June 30, 2023, led by products for jet engines. Additionally, we have a strong presence in the energy markets, including oil & gas, downstream processing, and specialty energy, as well as the medical and electronics markets. In aggregate, these markets represented approximately 83% of our revenue for the six months ended June 30, 2023. We are a market leader in manufacturing differentiated products that require our materials science capabilities and unique process technologies, including our new product development competence. Our capabilities range from cast/wrought and powder alloy development to final production of highly engineered finished components, including those used in next-generation jet engines and 3D-printed aerospace products.

We operate in two business segments, our High Performance Materials & Components (“HPMC”) segment and our Advanced Alloys & Solutions (“AA&S”) segment, which accounted for approximately 43% and 57%, respectively, of our total revenue in the year ended December 31, 2022 and approximately 48% and 52%, respectively, of our total revenue in the six months ended June 30, 2023.

High Performance Materials & Components

Our HPMC segment produces a wide range of high performance specialty materials, parts and components for several major end markets, including the aerospace & defense, medical, and energy markets. HPMC’s products are manufactured from a wide range of advanced materials including metallic powder alloys, made from nickel-based alloys and superalloys, titanium and titanium-based alloys, and a variety of other specialty materials. These materials are made into a variety of product forms that include precision forgings, machined parts and others. We are integrated across these alloy systems in melt, forging, finishing, testing and machining processes. Most of these products are sold directly to end-use customers, and a substantial portion of our HPMC segment products are sold under multi-year agreements.

Demand for HPMC’s products is driven primarily by the commercial aerospace cycle. Commercial aerospace products have been the main source of sales and EBITDA growth for HPMC over the last two years, and are expected to continue to drive HPMC and overall ATI results. Sales to the aerospace and defense markets comprised approximately 80% and 83% of HPMC revenue in the year ended December 31, 2022 and the six months ended June 30, 2023, respectively, including products for commercial jet engines, which accounted for approximately 60% of our HPMC segment’s total revenue in both the year ended December 31, 2022 and the six months ended June 30, 2023.

Large aircraft and jet engines are manufactured by a small number of companies, such as The Boeing Company and Airbus S.A.S. (an Airbus Group company) for airframes. GE Aerospace (a

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division of General Electric Company), Rolls-Royce plc, Pratt & Whitney (a division of Raytheon Technologies Corporation), Snecma (SAFRAN Group), and various joint ventures manufacture jet engines. These companies, and their suppliers, form a substantial portion of our customer base in this business segment. We have long-term agreements (“LTAs”) in place with most major aerospace market OEMs.

The HPMC segment’s principal competitors include: Berkshire Hathaway Inc., for nickel-based alloys and superalloys and specialty steel alloys, titanium and titanium-based alloys, and precision forgings through its ownership of Precision Castparts Corporation and subsidiaries; Howmet Aerospace Inc., for titanium and titanium-based alloys; Carpenter Technology Corporation for legacy nickel-based alloys and superalloys and specialty steel alloys; VSMPO-AVISMA for titanium and titanium-based alloys; and Aubert & Duval for precision forgings.

Advanced Alloys & Solutions Segment

Our AA&S segment is focused on delivering high-value flat products primarily to the energy, aerospace & defense end-markets, which comprised approximately 53% and 63% of its revenue in the year ended December 31, 2022 and the six months ended June 30, 2023, respectively. Other important end markets for AA&S include automotive and electronics. AA&S produces nickel-based alloys, titanium and titanium-based alloys, and specialty alloys in a variety of forms including plate, sheet, and Precision Rolled Strip^® (“PRS”) products. In December 2020, we announced a strategic repositioning of our Specialty Rolled Products (“SRP”) business, which was substantially completed in 2022 and included exiting production of lower-margin standard stainless sheet products, streamlining the production footprint of the AA&S segment and making certain capital investments to increase our focus on higher-margin products and our aerospace & defense end markets.

The major end markets for our flat rolled products are energy, aerospace & defense, automotive, and electronics markets. The operations in this segment include our SRP business, our Specialty Alloys & Components (“SA&C”) business and the Shanghai STAL Precision Stainless Steel Company Limited PRS joint venture in China, in which we hold a 60% interest. Segment results also include our 50% interest in the Uniti industrial titanium joint venture and our 50% interest in the A&T Stainless joint venture between us and an affiliate of Tsingshan Group (the “A&T Stainless joint venture”). In 2022, we announced the termination of the Uniti joint venture, which we expect to be dissolved in the third quarter of 2023. Additionally, in 2020, we indefinitely idled the manufacturing operations of the A&T Stainless joint venture.

Our SA&C business produces reactive and refractory metals such as hafnium, niobium, tantalum, titanium, vanadium and zirconium for use in various end markets and applications, ranging across aerospace, defense, missile and space (including hypersonics), energy, marine, medical, superconductivity and chemical and mineral processing. SA&C products are produced in a wide variety of forms such as ingot, forgings, billet, bar, rod, wire, extrusion, seamless pipe and tube, slab, plate, sheet, strip, foil, chemicals, powders, sponge and crystal bar. SA&C also produces custom shapes and near-net shape components. SA&C enables customers to meet stringent specifications and the metals needed for critical applications and extreme environments.

Competitors for nickel-based alloys and superalloys and specialty steel alloys include Haynes International and VDM Metals GmbH, a subsidiary of Acerinox S.A. We have exited the domestic commodity stainless sheet business.

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Our End Use Markets

Aerospace & Defense (Approximately 49% of 2022 revenue).  We are a world leader in the production of specialty materials and components for both commercial and military jet engines and airframes supporting customer needs for initial build requirements and for spare parts. Through alloy development, internal growth efforts, and long-term supply agreements on current and next-generation jet engines and airframes, we are well-positioned with a fully qualified asset base to meet the expected return to multi-year demand growth from the commercial aerospace market.

Typical aerospace applications for nickel-based alloys and superalloys and advanced metallic powders include jet engine discs, blades, vanes, rings, casings and shafts. Nickel-based alloys and superalloys remain extremely strong at high temperatures and resist degradation under extreme conditions. The next-generation jet engines use advanced nickel-based superalloys and metallic powder alloys to enable increased fuel efficiency requirements that require hotter-burning engines. Our specialty materials are also used in the manufacture of aircraft landing gear and structural components.

We are a global industry leader in iso-thermal and hot-die forging technologies for advanced aerospace components. In 2021, we completed capital investments for our fourth iso-thermal press and heat-treating capacity expansion at our Iso-Thermal Forging Center of Excellence in Cudahy, WI. We produce highly sophisticated components that have differing mechanical properties across a single product unit and are highly-resistant to fatigue and temperature effects. Our precision forgings are used for jet engine components, structural components for aircraft, helicopters, space propulsion, and other demanding applications. We provide a full range of post-production inspection and machining with the certified quality needed to meet demanding application requirements.

Products and components made from titanium and titanium-based alloys, such as jet engine components including discs, blades and vanes, and airframe components such as structural members, landing gears, and hydraulic systems, are critical in aerospace applications. These materials and components possess an extraordinary combination of properties that help to increase jet engine fuel efficiency and product longevity, including superior strength-to-weight ratios, elevated temperature resistance, low coefficient of thermal expansion, and extreme corrosion resistance.

Our specialty materials and components for defense applications include naval nuclear products, military jet engines, fixed wing and rotorcraft products, and armor applications. We expect to continue to increase our sales in government defense applications in future years.

We continuously seek to develop and manufacture innovative new alloys to better serve the needs of the aerospace & defense markets, and several of the alloys we produce have won significant share in the current and next-generation jet engines. Our metallic powder technology delivers alloy compositions and refined microstructures that offer increased performance and longer useful lives in high-temperature aerospace environments, and improve the efficiency of jet engines. We continue to increase our production capacity for advanced metallic powders for use in next-generation aerospace products, including additive manufacturing applications.

Energy (Approximately 20% of 2022 revenue).  We also serve energy markets, including specialty energy, oil & gas and downstream processing markets. Our specialty materials are widely used in the global electrical power generation and distribution industries. We believe clean energy needs, expanding environmental policies and the electrification of developing countries will continue to drive demand for our specialty materials and products for use in these industries over the long term.

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For electrical power generation, our specialty materials, including corrosion-resistant alloys (“CRAs”), are used in nuclear, natural gas and other fuel source applications. Our CRAs are used for pipe, tube, and heat exchanger applications in water systems and in pollution control scrubbers. For nuclear power plants, we are an industry pioneer in producing nuclear reactor fuel cladding and structural components utilizing zirconium and hafnium alloys. We are a technology leader for large diameter components used in natural gas land-based turbines for power generation. Our alloys are also used for alternative energy generation, in solar, fuel cell and geothermal applications.

Both of our business segments produce specialty materials that are critical to the oil & gas industry. The environments in which oil & gas can be found in commercial quantities have become more challenging, involving deep offshore wells, high pressure and high temperature conditions in sour wells and unconventional sources. These challenging offshore environments are located further off the continental shelf, including locations in arctic and tropical waters where drilling is more difficult than previously-sourced locations. Our specialty materials, including nickel-based alloys, duplex alloys and other specialty alloys, have the strength and corrosion-resistant properties necessary to meet these challenging operating conditions. We enable our customers’ success in these applications by developing and producing specialty materials for equipment that can operate for up to 30 years in these harsh environments.

Medical (Approximately 4% of 2022 revenue).  Our advanced specialty materials are used in medical device products that enhance the quality of lives around the world. Manufacturers of magnetic resonance imaging (“MRI”) devices rely on our niobium superconducting wire to help produce electromagnetic fields that allow physicians to safely scan the body’s soft tissue. We have a joint technology development agreement with Bruker Energy & Supercon Technologies to advance state-of-the-art niobium-based superconductors, including those used in MRI magnets for the medical industry, and preclinical MRI magnets used in the life-science tools industry.

Our specialty alloys also are used for replacement knees, hips and other prosthetic devices. The use of our alloys in these replacement devices offers the potential for longer product lifespans versus previous implant generations.

Our biocompatible nickel-titanium shape memory alloy is used for stents to support collapsed or clogged blood vessels. Reduced in diameter for insertion, these stents expand post-implant to the original tube-like shape due to the metal’s superelasticity. In addition, our ultra-fine diameter (0.002 inch/0.051 mm) titanium wire is used for screens to prevent blood clots from entering critical areas of the body.

Electronics (Approximately 5% of 2022 revenue).  Our materials perform a variety of important roles in the growing consumer electronics market. Nickel alloys and PRS from SRP and our Asian PRS joint venture support computers and smart phones. The magnetic properties of nickel alloys are used in relay cores, magnets and magnetic shielding, while their thermal expansion is useful in glass-to-metal sealing applications such as monitors. PRS is selected for electronics and communications applications based on corrosion resistance, strength, wear resistance, electrical resistivity or thermal expansion properties.

In addition, metal precursors – which use chemicals produced by us, such as hafnium – have a variety of important applications in consumer and industrial electronics.

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Our Competitive Advantages

We are a market leader in manufacturing differentiated products that require our materials science capabilities and unique process technologies, including our new product development competence. Our diverse and differentiated product line requires a multitude of capabilities that allows us to provide comprehensive customer solutions. The process capabilities of our diverse product portfolio are set forth below:

Backlog

We maintained a backlog of confirmed orders totaling approximately $3.5 billion and $2.9 billion at June 30, 2023 and December 31, 2022, respectively. Due to the structure of our LTAs, approximately 70% of our backlog at June 30, 2023 represented booked orders with performance obligations that we expect to be satisfied within the next 12 months. The backlog does not reflect any elements of variable consideration.

Our HPMC segment’s backlog of confirmed orders was approximately $2.3 billion at December 31, 2022 and $1.6 billion at December 31, 2021. We expect that approximately 75% of the confirmed orders on hand at December 31, 2022 for this segment will be filled during the year ending December 31, 2023. Our AA&S segment’s backlog of confirmed orders was approximately $0.6 billion at December 31, 2022 and $0.5 billion at December 31, 2021. We expect that nearly 100% of the confirmed orders on hand at December 31, 2022 for this segment will be filled during the year ending December 31, 2023.

Raw Materials and Supplies

Substantially all raw materials and supplies required in the manufacture of our products are available from more than one supplier, and the sources and availability of raw materials essential to our businesses are currently adequate. The principal raw materials we use in the production of our specialty materials are scrap (including iron-, nickel-, chromium-, titanium-, and molybdenum-bearing scrap), nickel, titanium sponge, zirconium sand and sponge, ferrochromium, ferrosilicon, molybdenum and molybdenum alloys, manganese and manganese alloys, cobalt, niobium, vanadium and other alloying materials. While we enter into raw materials futures contracts from time to time to hedge exposure to price fluctuations, such as for nickel, we cannot be certain that our hedge position adequately reduces exposure. We believe that we have adequate controls to monitor these contracts, but we may not be able to accurately assess exposure to price volatility in the markets for critical raw materials.

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Some raw materials, such as nickel, cobalt, and ferrochromium, are available to us and our specialty materials industry competitors primarily from foreign sources. Some of these foreign sources are located in countries that may be subject to unstable political and economic conditions, which could disrupt supplies or affect the price of these materials.

We purchase our nickel requirements principally from producers in Australia, Canada, Norway, Russia and the Dominican Republic. We purchase zirconium raw materials primarily domestically and also from producers in China. Cobalt is purchased primarily from producers in Canada. More than 80% of the world’s reserves of ferrochromium are located in South Africa, Zimbabwe, Albania and Kazakhstan. Niobium is purchased principally from producers in Brazil, and our titanium sponge comes from sources in Japan and Kazakhstan.

Certain key supplies used in melting and other processing operations, such as graphite electrodes and industrial gases including helium and argon, are from time-to-time limited in availability and may be subject to significant price inflation. We enter into long-term supply contracts where possible to ensure an adequate supply of these products; however, overall industry shortages may impact our operations and scheduling.

Organizational Structure

The following diagram depicts (on a condensed basis) our anticipated corporate structure as of June 30, 2023 after giving effect to the issuance of the notes offered hereby:

(1) ATI Inc. is a guarantor of the 6.95% Debentures due 2025 issued by Allegheny Ludlum, LLC and a guarantor under our existing senior secured credit facilities.

(2) Allegheny Operating Holdings, LLC and certain of our other domestic subsidiaries are guarantors under our existing senior secured credit facilities.

(3) Allegheny Ludlum, LLC and certain of our other domestic subsidiaries are borrowers under our existing senior secured credit facilities.

(4) Our asset-based revolving credit facility provides for aggregate borrowings of up to $600 million. Borrowing availability under the facility is reduced on a dollar-for-dollar basis by the amount of any outstanding letters of credit under the facility. As of June 30, 2023, we had $50.0 million of outstanding borrowings under the facility, and $39.4 million of letters of credit were outstanding under the facility.

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Corporate Information

We were incorporated in Delaware in 1996. Our principal executive offices are located at 2021 McKinney Avenue, Suite 1100, Dallas, Texas, telephone (800) 289-7454. Our website address is www.ATImaterials.com. The information on or accessible through our website does not constitute part of this prospectus supplement or the accompanying prospectus.

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The Offering

Issuer ATI Inc.

Securities Offered $425,000,000 aggregate principal amount of our 7.250% Senior Notes due 2030.

Maturity The notes will mature on August 15, 2030, unless earlier redeemed or repurchased.

Interest Rate The notes will bear interest at 7.250 percent per year.

Interest Payment Dates February 15 and August 15 of each year, beginning on February 15, 2024.

Optional Redemption Prior to August 15, 2026, we may redeem the notes at our option, at any time in whole or from time to time in part, at a redemption price equal to 100% of the principal amount of the notes redeemed plus the Applicable Premium (as defined herein) as of, and accrued and unpaid interest to, but not including, the redemption date (subject to the right of holders of record on the relevant record date to receive interest due on the relevant interest payment date).

On and after August 15, 2026, we may redeem the notes at our option, at any time in whole or from time to time in part, at the redemption prices set forth in this prospectus supplement, plus accrued and unpaid interest to, but not including, the redemption date, on the principal amount of the notes to be redeemed to such redemption date. See “Description of Notes — Optional Redemption.”

In addition, at any time prior to August 15, 2026, we may, at our option and at any time, redeem up to 40.0% of the aggregate principal amount of notes at a redemption price equal to 107.250% of the aggregate principal amount thereof, plus accrued and unpaid interest to, but not including, the redemption date, on the principal amount of the notes to be redeemed to such redemption date, with the net proceeds of one or more Equity Offerings (as defined herein); provided that at least 60% of the aggregate principal amount of notes remain outstanding immediately after the occurrence of each such redemption. See “Description of Notes — Optional Redemption.”

Offer to Repurchase upon a Change of Control Repurchase Event If a change of control repurchase event occurs with respect to the notes, we will be required, subject to certain conditions, to offer to repurchase the notes at a purchase price equal to 101%

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of the principal amount of the notes repurchased, plus accrued and unpaid interest to, but not including, the date of repurchase. See “Description of Notes — Purchase of Notes upon a Change of Control Repurchase Event.”

Covenants We will issue the notes under a senior indenture between us and Computershare Trust Company, N.A., as successor trustee to Wells Fargo Bank, National Association. The senior indenture includes covenants that limit:

• our ability and the ability of our domestic subsidiaries to create or permit liens;

• our ability and the ability of our domestic subsidiaries to enter into sale and leaseback transactions;

• the ability of our domestic subsidiaries to guarantee our indebtedness; and

• our ability to consolidate or merge with or into other companies or sell all or substantially all of our assets.

These covenants will be subject to a number of important exceptions and qualifications described under “Description of Notes — Covenants” and “Description of Notes — Merger, Consolidation or Sale of Assets.”

Events of Default If there is an event of default under the notes, the principal amount of the notes, plus accrued and unpaid interest, may be declared immediately due and payable. These amounts automatically become due and payable if an event of default relating to certain events of bankruptcy, insolvency or reorganization occurs.

Ranking The notes will be our senior unsecured obligations, ranking equally in right of payment with all of our existing and future senior unsecured indebtedness and senior to our future subordinated indebtedness. The notes will be effectively subordinated to our existing and future secured indebtedness to the extent of the value of the assets securing that indebtedness and to the existing and future indebtedness and other liabilities of our subsidiaries. We conduct a significant portion of our business through our subsidiaries. None of our subsidiaries will guarantee the notes.

As of June 30, 2023, after giving effect to this offering, we would have had an aggregate of approximately $2.2 billion of indebtedness outstanding, $250 million of which would have been secured. As of June 30, 2023, our subsidiaries had an

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aggregate of approximately $469 million of indebtedness outstanding, principally comprised of the $200 million term loan outstanding under our existing senior secured credit facilities and $150 million in unsecured 6.95% Debentures due 2025 issued by our wholly owned subsidiary Allegheny Ludlum LLC and guaranteed by ATI. In addition, our subsidiaries had the ability to borrow an additional approximately $500 million under our existing senior secured credit facilities as of June 30, 2023, which borrowings would be secured. See “Summary — Organizational Structure” and “Risk Factors.”

Use of Proceeds We intend to use up to approximately $300 million of the net proceeds from this offering to fund our pension liabilities and to implement pension derisking strategies, potentially including annuitizations. We intend to use any remaining net proceeds from this offering for liquidity and general corporate purposes. See “Use of Proceeds.”

Book-Entry Form The notes will be issued in book-entry form and will be represented by permanent global certificates deposited with, or on behalf of, DTC and registered in the name of a nominee of DTC. Investors may elect to hold interests in the notes through DTC, Clearstream or Euroclear if they are participants of such systems, or indirectly through organizations which are participants in such systems. Beneficial interests in the notes will be shown on, and transfers will be effected only through, records maintained by DTC or its nominee, and any such interests may not be exchanged for certificated securities, except in limited circumstances.

Absence of Public Market for the Notes The notes are new securities, and there is currently no established market for the notes. Accordingly, we cannot assure you as to the development or liquidity of any market for the notes. The underwriters have advised us that they currently intend to make a market in the notes. However, they are not obligated to do so, and they may discontinue any market making with respect to the notes without notice.

Material U.S. Federal Income Tax Considerations Holders are urged to consult their own tax advisors with respect to the U.S. federal, state, local and non-U.S. tax consequences of purchasing, owning and disposing of the notes. See “Material U.S. Federal Income Tax Considerations.”

Trustee Computershare Trust Company, N.A.

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Risk Factors You should carefully consider the information set forth in the section entitled “Risk Factors” and the other information included or incorporated by reference into this prospectus supplement and the accompanying prospectus in deciding whether to purchase the notes.

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Summary Consolidated Financial Data

We derived the summary consolidated financial data shown below as of December 31, 2020, 2021 and 2022 and for each of the years then ended from our audited consolidated financial statements. We derived the summary consolidated financial data as of June 30, 2023 and 2022 and for each of the six-month periods then ended from our unaudited consolidated financial statements. The unaudited consolidated financial statements from which we derived this data were prepared on the same basis as the audited consolidated financial data and include all adjustments, consisting only of normal recurring adjustments, necessary to present fairly our consolidated results of operations and financial condition as of the periods presented. The results of operations for interim periods are not necessarily indicative of the operating results for any future period. You should read the following financial information in conjunction with “Management’s Discussion and Analysis of Financial Condition and Results of Operations” and our consolidated financial statements and the related notes in our Annual Report on Form 10-K for the fiscal year ended December 31, 2022 and our Quarterly Report on Form 10-Q for the fiscal quarter ended June 30, 2023, which are incorporated by reference into this prospectus supplement and the accompanying prospectus.

	Year Ended December 31,						Six Months Ended June 30,
	2020		2021		2022		2022		2023
	(Dollars in millions)
							(Unaudited)
Statement of operations data:
Sales	$	2,982.1	$	2,799.8	$	3,836.0	$	1,793.6	$	2,084.1
Cost of sales		2,689.3		2,466.6		3,121.8		1,448.9		1,681.8
Gross profit	$	292.8	$	333.2	$	714.2	$	344.7	$	402.3
Selling and administrative expenses		201.0		226.9		297.5		147.5		166.0
Impairment of goodwill		287.0		—		—		—		—
Restructuring charges (credits)		1,107.5		(11.3)		(4.8)		(2.4)		2.7
Loss on asset sales and sales of businesses, net		—		—		134.2		134.2		0.7
Operating income (loss)	$	(1,302.7)	$	117.6	$	287.3	$	65.4	$	232.9
Nonoperating retirement benefit expense		(62.1)		37.2		(25.4)		(12.4)		(33.7)
Interest expense, net		(94.4)		(96.9)		(87.4)		(47.0)		(41.2)
Debt extinguishment charge		(21.5)		(65.5)		—		—		—
Other income (loss), net		(1.2)		18.2		(12.5)		3.2		1.3
Income (loss) before income taxes	$	(1,481.9)	$	10.6	$	162.0	$	9.2	$	159.3
Income tax provision		77.7		26.8		15.5		8.3		8.0
Net income (loss)	$	(1,559.6)	$	(16.2)	$	146.5	$	0.9	$	151.3
Less: Net income attributable to noncontrolling interests		13.0		22.0		15.6		8.0		5.2
Net income (loss) attributable to ATI	$	(1,572.6)	$	(38.2)	$	130.9	$	(7.1)	$	146.1
Balance sheet data (at end of period):
Working capital	$	1,412.7	$	1,450.3	$	1,512.5	$	1,511.8	$	1,561.1
Total assets		4,034.9		4,285.2		4,445.6		4,229.4		4,434.7
Long-term debt		1,550.0		1,711.6		1,706.3		1,703.3		1,699.9
Total debt1		1,629.1		1,863.7		1,765.2		1,754.8		1789.3
Cash and cash equivalents		645.9		687.7		584.0		274.0		267.1
Total ATI stockholders’ equity		521.1		685.6		1,045.9		762.9		1,194.0

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	Year Ended December 31,						Six Months Ended June 30,
	2020		2021		2022		2022		2023
	(Dollars in millions)
							(Unaudited)
Cash flow information:
Cash flow provided by (used in) operating activities	$	166.9	$	16.1	$	224.9	$	(222.4)	$	(217.1)
Cash flow provided by (used in) investing activities		(128.7)		(77.3)		(126.7)		(55.7)		(100.8)
Cash flow provided by (used in) financing activities		116.9		103.0		(201.9)		(135.6)		1.0
Purchase of property, plant and equipment		(136.5)		(152.6)		(130.9)		(54.8)		(103.3)
Other data:
EBITDA (unaudited)2	$	(1,244.2)	$	251.4	$	392.3	$	127.7	$	271.5
Adjusted EBITDA (unaudited)2	$	196.3	$	290.9	$	549.3	$	268.1	$	282.5

(1) Excludes debt issuance costs and equity component of convertible debt.

(2) We define EBITDA as net income before interest expense and income taxes, plus depreciation and amortization. We define Adjusted EBITDA as EBITDA excluding significant charges or credits, including goodwill impairment charges and restructuring charges including long-lived asset impairments. EBITDA and Adjusted EBITDA are not measures of financial performance under generally accepted accounting principles. EBITDA and Adjusted EBITDA are not calculated in the same manner by all companies and, accordingly, are not necessarily comparable to similarly titled measures of other companies and may not be an appropriate measure of performance relative to other companies. Interest expense, net as presented includes reductions for interest expense capitalized on construction in progress and is net of interest income. We have presented EBITDA and Adjusted EBITDA in this prospectus supplement solely as supplemental disclosures because we believe they allow for a more complete analysis of our results of operations. We believe that EBITDA and Adjusted EBITDA are useful to investors because EBITDA and Adjusted EBITDA are commonly used to analyze companies on the basis of operating performance, leverage and liquidity. Furthermore, analogous measures are used by industry analysts to evaluate operating performance. EBITDA and Adjusted EBITDA are not intended to be measures of free cash flow for management’s discretionary use, as they do not consider certain cash requirements such as interest payments, tax payments and capital expenditures. EBITDA and Adjusted EBITDA are not intended to represent, and should not be considered more meaningful than, or as alternatives to, a measure of operating performance as determined in accordance with generally accepted accounting principles. The definitions of EBITDA and Adjusted EBITDA will differ from the amounts calculated under the definition of Consolidated EBITDA that is contained in our currently outstanding credit facility. EBITDA and Adjusted EBITDA are calculated as follows:

	Year Ended December 31,						Six Months Ended June 30,
	2020		2021		2022		2022		2023
	(Dollars in millions)
	(Unaudited)
Net income (loss) attributable to ATI . . . .	$	(1,572.6)	$	(38.2)	$	130.9	$	(7.1)	$	146.1
Net income attributable to noncontrolling interests		13.0		22.0		15.6		8.0		5.2
Net income (loss)		(1,559.6)		(16.2)		146.5		0.9		151.3
Interest expense, net		94.4		96.9		87.4		47.0		41.2
Income tax provision (benefit)		77.7		26.8		15.5		8.3		8.0
Depreciation and amortization		143.3		143.9		142.9		71.5		71.0
EBITDA		(1,244.2)		251.4		392.3		127.7		271.5
Debt extinguishment charge(a)		21.5		65.5		—		—		—
Restructuring and other charges (credits)(b)		1,132.1		(10.5)		23.7		6.2		10.4
Impairment of goodwill(c)		287.0		—		—		—		—
Retirement benefit settlement gain(d)		—		(64.9)		—		—		—
Loss (gain) on asset sales and sales of businesses, net(e)		(2.5)		(13.8)		134.2		134.2		0.6
Strike related costs(f)		—		63.2		—		—		—
Joint venture restructuring charges (credit)(g)		2.4		—		(0.9)		—		—
Adjusted EBITDA	$	196.3	$	290.9	$	549.3	$	268.1	$	282.5

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(a) The debt extinguishment charge for the year ended December 31, 2020 was for the repurchase of a portion of our 4.75% Convertible Senior Notes due 2022. The debt extinguishment charge for the year ended December 31, 2021 was for the full redemption of our 5.875% Senior Notes due 2023.

(b) Results for the year ended December 31, 2020 include $1,132.1 million in pre-tax restructuring and other charges consisting of $1,041.5 million of long-lived asset impairment charges primarily related to the AA&S segment’s Brackenridge, PA operations, $33.5 million of severance-related costs for hourly and salary employees, $27.0 million of severance charges for involuntary reductions and voluntary retirement incentive programs, $12.7 million of other costs related to facility idlings including asset retirement obligations and inventory valuation reserves, and $17.4 million in pre-tax charges for termination benefits for pension and postretirement medical obligations related to facility closures. The restructuring credit for the year ended December 31, 2021 is primarily related to lowered severance-related reserves based on changes in planned operating rates and revised workforce reduction estimates. Results for the year ended December 31, 2022 includes a $28.5 million pre-tax litigation reserve, partially offset by a $4.8 million pre-tax credit for restructuring charges, primarily related to lowered severance-related reserves based on changes in planned operating rates and revised workforce reduction estimates. Results for the six months ended June 30, 2022 include a $2.4 million pre-tax credit for restructuring charges, primarily related to lowered severance-related reserves based on changes in planned operating rates and revised workforce reduction estimates, and an $8.6 million pre-tax litigation reserve for the subsequently settled case of US Magnesium, LLC v. ATI Titanium LLC, a subsidiary of ATI. Results for the six months ended June 30, 2023 include pre-tax charges totaling $10.4 million, which include $5.7 million for start-up costs, $2.7 million of severance-related restructuring charges, and $2.0 million primarily for asset write-offs related to the closure of our Robinson, PA operation.

(c) The goodwill impairment for the year ended December 31, 2020 was for a pre-tax goodwill impairment charge to write-off a portion of our goodwill related to our Forged Products reporting unit.

(d) The retirement benefit settlement gain in the year ended December 31, 2021 includes a $64.9 million pre-tax retirement benefit settlement gain associated with a new collective bargaining agreement that was ratified in July 2021 with the United Steel, Paper and Forestry, Rubber, Manufacturing, Energy, Allied & Industrial Service Workers International Union, AFL-CIO, CLC involving approximately 1,100 active full-time represented employees located primarily within the AA&S segment operations, as well as a number of inactive employees.

(e) Results for the year ended December 31, 2020 include a gain on the sale of oil & gas rights in New Mexico. Results for the year ended December 31, 2021 include a $13.8 million pre-tax gain on the sale of our Flowform Products business. Results for the year ended December 31, 2022 and the six months ended June 30, 2022 include a $141.0 million loss on the sale of our Sheffield, UK operations. This loss includes $55.6 million related to the UK defined benefit pension plan, of which $26.1 million was reported as a net pension asset and $29.5 million in accumulated other comprehensive loss, and $20.0 million of cumulative translation adjustment foreign exchange losses. This loss was offset by $6.8 million pre-tax gain on the sale of our small Pico Rivera, CA operations as part of the strategy to exit standard stainless products. Results for the six months ended June 30, 2023 include a $0.6 million loss on the sale of our Northbrook, IL operation.

(f) The strike related costs for the year ended December 31, 2021 include $63.2 million of pre-tax costs primarily consisting of overhead costs recognized in the period due to below-normal operating rates, higher costs for outside conversion activities and signing bonuses for represented employees.

(g) The joint venture restructuring charges for the year ended December 31, 2020 include a $2.4 million pre-tax charge for our 50% portion of severance charges recorded by the A&T Stainless joint venture. The joint venture restructuring credit in the year ended December 31, 2022 is a $0.9 million pre-tax credit for our 50% portion of the A&T Stainless joint venture’s credit for restructuring charges.

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RISK FACTORS

You should carefully consider the following factors and those described in our Annual Report on Form 10-K for our fiscal year ended December 31, 2022 and any of our subsequently filed Quarterly Reports on Form 10-Q, as well as the other information contained or incorporated by reference in this prospectus supplement and the accompanying prospectus, before deciding to invest in the notes. Any of these risks or other risks and uncertainties not presently known to us or that we currently deem immaterial could materially adversely affect our business, financial condition, results of operations and cash flow, which could in turn materially adversely affect the price of the notes. If any of the following risks and uncertainties develop into actual events, our business, financial condition, results of operations or cash flows could be materially adversely affected. In that case, the trading price of the notes could decline and you may lose all or part of your investment.

This prospectus supplement also contains forward-looking statements that involve risks and uncertainties. Our actual results could differ materially from those anticipated in these forward-looking statements as a result of the risks faced by us described below and elsewhere in this prospectus supplement, the accompanying prospectus and the documents incorporated by reference. Please see “Forward-Looking Statements.”

Risks Relating to the Notes

Our substantial indebtedness could adversely affect our business, financial condition or results of operations and prevent us from fulfilling our obligations under the notes.

We currently have and, after this offering, will continue to have a significant amount of indebtedness. As of June 30, 2023, after giving effect to this offering, our total consolidated indebtedness would have been approximately $2.2 billion (excluding accounts payable, accrued expenses, other liabilities, variable interest entity liabilities and unfunded commitments). Our subsidiaries had the ability to borrow an additional approximately $500 million under our revolving credit facility as of June 30, 2023. This substantial level of indebtedness increases the risk that we may be unable to generate enough cash to pay amounts due in respect of our indebtedness, including the notes.

Our substantial indebtedness could have important consequences to you and significant effects on our business. For example, it could:

• make it more difficult for us to satisfy our obligations with respect to the notes;

• increase our vulnerability to general adverse economic and industry conditions;

• require us to dedicate a substantial portion of our cash flow from operations to payments on our indebtedness, thereby reducing the availability of our cash flow to fund working capital, capital expenditures, our strategic growth initiatives and development efforts and other general corporate purposes;

• limit our flexibility in planning for, or reacting to, changes in our business and the industry in which we operate;

• restrict us from exploiting business opportunities;

• place us at a competitive disadvantage compared to our competitors that have less indebtedness; and

• limit our ability to borrow additional funds for working capital, capital expenditures, acquisitions, debt service requirements, execution of our business strategy or other general corporate purposes.

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In addition, the agreements that govern our current indebtedness contain, and the agreements that may govern any future indebtedness that we may incur may contain, financial and other restrictive covenants that will limit our ability to engage in activities that may be in our long-term best interests. Our failure to comply with those covenants could result in an event of default that, if not cured or waived, could result in the acceleration of all of our debt.

Despite our substantial current indebtedness, we and our subsidiaries may still be able to incur substantially more indebtedness. This could further exacerbate the risks associated with our substantial leverage.

We and our subsidiaries may be able to incur substantial additional indebtedness in the future, including pursuant to a capital markets transaction such as a notes offering, as well as additional secured indebtedness that would be structurally or effectively senior to the notes. Furthermore, neither the base indenture nor the supplemental indenture establishing the terms of the notes will limit the amount of debt that we or our subsidiaries may issue. As of June 30, 2023, after giving effect to this offering, we and our subsidiaries would have had approximately $2.2 billion of total indebtedness outstanding on a consolidated basis. In addition, our subsidiaries had the ability to borrow an additional approximately $500 million under our revolving credit facility as of June 30, 2023. Adding new indebtedness to current debt levels could make it more difficult for us to satisfy our obligations with respect to the notes.

Repayment of our debt, including the notes, is dependent on cash flow generated by our subsidiaries.

Our subsidiaries own a significant portion of our assets and conduct a significant portion of our operations. Accordingly, repayment of our indebtedness, including the notes, is dependent, to a significant extent, on the generation of cash flow by our subsidiaries and their ability to make such cash available to us, by dividend, debt repayment or otherwise. None of our subsidiaries will initially guarantee the notes. Our subsidiaries do not have any obligation to pay amounts due on the notes or to make funds available for that purpose. Our subsidiaries may not be able to, or may not be permitted to, make distributions to enable us to make payments in respect of our indebtedness, including the notes. Each subsidiary is a distinct legal entity and, under certain circumstances, legal and contractual restrictions may limit our ability to obtain cash from our subsidiaries. In the event that we do not receive distributions from our subsidiaries, we may be unable to make required principal and interest payments on our indebtedness, including the notes. As of June 30, 2023, our subsidiaries had approximately $469 million of total indebtedness outstanding and the ability to borrow an additional approximately $500 million under our revolving credit facility, to which the notes would have been structurally subordinated.

The notes will be structurally subordinated to all liabilities of our subsidiaries.

The notes will initially not be guaranteed by any of our subsidiaries and are therefore structurally subordinated to the indebtedness and other liabilities of our subsidiaries. These subsidiaries are separate and distinct legal entities and have no obligation, contingent or otherwise, to pay any amounts due pursuant to the notes, or to make any funds available therefor, whether by dividends, loans, distributions or other payments. Any right that we have to receive any assets of any of the subsidiaries upon the liquidation or reorganization of those subsidiaries, and the consequent rights of holders of notes to realize proceeds from the sale of any of those subsidiaries’ assets, will be effectively subordinated to the claims of those subsidiaries’ creditors, including trade creditors and holders of preferred equity interests of those subsidiaries. Accordingly, in the event of a bankruptcy, liquidation

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or reorganization of any of our subsidiaries, these subsidiaries will pay the holders of their debts, holders of preferred equity interests and their trade creditors before they will be able to distribute any of their assets to us. As of June 30, 2023, our subsidiaries had an aggregate of approximately $469 million of indebtedness outstanding, principally comprised of the $200 million term loan outstanding under our existing senior secured credit facilities and $150 million in unsecured 6.95% Debentures due 2025 issued by our wholly owned subsidiary Allegheny Ludlum LLC and guaranteed by ATI. In addition, our subsidiaries had the ability to borrow an additional approximately $500 million under our existing senior secured credit facilities as of June 30, 2023, which borrowings would be secured.

The notes are subject to prior claims of secured creditors.

The notes will be unsecured, ranking equally in right of payment with our other unsecured and unsubordinated indebtedness and will be effectively subordinated in right of payment to any of our secured indebtedness, to the extent of the value of the assets securing such indebtedness. Our obligations under our existing credit facility are secured by each loan party’s respective (i) accounts receivable and inventory and (ii) solely to the extent related to such accounts receivable and inventory, proceeds, supporting obligations, chattel paper, documents, electronic chattel paper, general intangibles, instruments, deposit accounts, commercial tort claims and letter-of-credit rights. Additionally, we have an option to include certain machinery and equipment as additional collateral for purposes of determining availability under our existing credit facility. The base indenture and supplemental indenture governing the notes and the credit agreement governing our existing credit facility permit us to incur secured indebtedness under specified circumstances, and the amounts incurred could be substantial. If we incur any indebtedness secured by our assets, these assets could be subject to the prior claims of secured creditors. As of June 30, 2023, after giving effect to this offering, we would have had approximately $2.2 billion of total indebtedness outstanding, $200.0 million of which is secured. As of June 30, 2023, our subsidiaries had an aggregate of approximately $469 million of indebtedness outstanding, principally comprised of the $200 million term loan outstanding under our existing senior secured credit facilities and $150 million in unsecured 6.95% Debentures due 2025 issued by our wholly owned subsidiary Allegheny Ludlum LLC and guaranteed by ATI. In addition, our subsidiaries had the ability to borrow an additional approximately $500 million under our revolving credit facility as of June 30, 2023, which borrowings would be secured.

In the event of a bankruptcy, liquidation or similar proceeding, our pledged assets would be available to satisfy obligations of the secured indebtedness before any payment could be made on the notes. As a result, the notes will be effectively subordinated to any secured indebtedness that we may have. To the extent that such pledged assets cannot satisfy such secured indebtedness, the holders of such indebtedness would have a claim for any shortfall that would rank equally in right of payment with the notes.

Some significant transactions may not constitute a change of control repurchase event for purposes of the notes in which case we would not be obligated to offer to repurchase the notes.

Upon the occurrence of a change of control repurchase event as described under “Description of Notes — Purchase of Notes upon a Change of Control Repurchase Event,” we will be required to offer to repurchase the notes. However, the change of control repurchase event provisions will not afford protection to holders of notes in the event of certain transactions. For example, any leveraged recapitalization, refinancing, restructuring or acquisition initiated by us will generally not constitute a change of control repurchase event requiring us to repurchase the notes. In the event of any such

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transaction, we will not be required to offer to repurchase the notes, even though any of these transactions could increase the amount of our indebtedness, or otherwise adversely affect our capital structure or credit ratings, thereby adversely affecting the holders of notes, including by decreasing the trading prices for the notes.

You may not be able to determine when a change of control repurchase event has occurred.

Unless we have exercised our right to redeem the notes, a change of control repurchase event, as defined in the indenture governing the notes, will require us to make an offer to repurchase all outstanding notes. The definition of change of control includes a phrase relating to the sale, lease or transfer or conveyance of “all or substantially all” of our assets. There is no precisely established definition of the phrase “substantially all” under applicable law. Accordingly, your ability to require us to repurchase your notes as a result of a sale, lease or transfer of less than all of our assets to another individual, group or entity may be uncertain. See “Description of Notes — Purchase of Notes upon a Change of Control Repurchase Event.”

We may not be able to repurchase the notes upon a change of control repurchase event.

Upon a change of control repurchase event, as defined in the indenture governing the notes, we will be required to make an offer to repurchase all outstanding notes at 101% of their principal amount, plus accrued and unpaid interest, unless we have previously given notice of our intention to exercise our right to redeem the notes. We may not have sufficient financial resources to purchase all of the notes that are tendered upon a change of control offer or to redeem the notes. A failure to make the applicable change of control offer or to pay the applicable change of control purchase price when due would result in a default under the indenture. The occurrence of a change of control repurchase event would also constitute an event of default under our revolving credit facility and may constitute an event of default under the terms of the agreements governing our other indebtedness. See “Description of Notes — Purchase of Notes upon a Change of Control Repurchase Event.”

The notes do not contain restrictive covenants requiring us to maintain any minimum financial results, and we may incur substantially more debt or take other actions that ultimately may affect our ability to satisfy our obligations under the notes.

Other than as described in this prospectus supplement under “Description of Notes — Covenants” and in the accompanying prospectus under “Description of Notes — Merger, Consolidation or Sale of Assets,” the notes are not subject to any restrictive covenants, and we are not restricted from paying dividends or issuing or repurchasing our securities. In addition, the limited covenants applicable to the notes do not require us to achieve or maintain any minimum financial results relating to our financial position or results of operations.

Our ability to recapitalize, incur additional debt, and take a number of other actions that are not limited by the terms of the notes could have the effect of diminishing our ability to make payments on the notes when due, and require us to dedicate a substantial portion of our cash flow from operations to make payments on our indebtedness, which would reduce the availability of cash flow to fund our operations, working capital and capital expenditures.

Further, holders of the notes should have a reasonable expectation that, subject to certain exceptions described in the indenture, the base indenture or the supplemental indenture establishing the terms of the notes, or the notes themselves, may be amended, supplemented or waived from time to time in accordance with their respective terms and that such amendments, supplements or waivers will be binding on all holders of the notes. See “Description of Debt Securities — Modifications and

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Waivers” in the accompanying prospectus. For these reasons, you should not consider any covenants in the base indenture or the supplemental indenture establishing the terms of the notes as a significant factor in evaluating whether to invest in the notes.

Our board of directors may determine that a property of ours is not a Principal Property (as defined in the supplemental indenture) and therefore not subject to certain covenants applicable to the notes.

The supplemental indenture governing the notes will include covenants that, among other things, limit our ability to issue, assume or guarantee any indebtedness if that indebtedness is secured by any lien upon any Principal Property (as defined in the supplemental indenture), or portion thereof, of ours without effectively securing the notes equally and ratably with that indebtedness, so long as such indebtedness is so secured. Such covenants are the only limit in the notes on our ability to incur secured debt that would be effectively senior to the notes to the extent of the value of the collateral. See “Description of Notes — Covenants.” The supplemental indenture will provide that a Principal Property means any manufacturing plant or other similar facility owned by us, the book value of the real property, plant and equipment of which (as shown, without deduction of any depreciation reserves, on the books of the owner or owners) is not less than two percent of Consolidated Net Tangible Assets (as defined in the supplemental indenture) except (A) any such plant or facility which our board of directors determines is not of material importance to the total business conducted, or assets owned, by us as an entirety or (B) any portion of any such plant or facility which our board of directors determines not to be of material importance to the use or operation thereof. Although it has not yet done so, under the terms of the supplemental indenture governing the notes, our board of directors may determine from time to time after the issuance of the notes that a property of ours is not of material importance to the total business conducted, or assets owned, by us and our U.S. domestic, consolidated subsidiaries as an entirety and, therefore, is not a Principal Property, meaning that such property would no longer be subject to the covenant in the supplemental indenture that limits our ability to incur indebtedness secured by a lien on that property. Any such secured indebtedness incurred by us would be effectively and/or structurally senior to the notes.

There may be no active trading market for the notes.

The notes are a new issue of securities for which there is no established market. Accordingly, any or all of the following may occur:

• no liquid market for the registered notes may develop;

• you may be unable to sell your notes; or

• the price at which you will be able to sell the notes may be lower than their principal amount or purchase price.

If a public market were to exist, the notes could trade at prices that may be higher or lower than their principal amount or purchase price, depending on many factors, including prevailing interest rates, the market for similar notes, the then-current ratings assigned to the notes and our financial performance. We do not intend to list the notes on any securities exchange or to seek approval for quotations through any automated quotation system. No active market for the notes is currently anticipated.

Redemption may adversely affect your return on the notes.

We have the right to redeem the notes prior to maturity, as described under “Description of Notes — Optional Redemption” in this prospectus supplement. We may redeem the notes at times when

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prevailing interest rates may be relatively low. Accordingly, you may not be able to reinvest the redemption proceeds in a comparable security at an effective interest rate as high as the interest rate of the notes being redeemed.

Future funding requirements may affect our business.

New sources of capital may be needed to meet the funding requirements of future investments in operating assets or other acquisitions, fund our ongoing business activities and pay dividends. Our ability to raise and service significant new sources of capital will be a function of macroeconomic conditions, future prices as well as our operational performance, cash flow and debt position, among other factors. We may determine that it may be necessary or preferable to issue additional debt or other securities, defer projects or sell assets. Additional financing may not be available when needed or, if available, the terms of such financing may not be favorable to us. In the event of lower prices, unanticipated operating or financial challenges, or new funding limitations, our ability to pursue new business opportunities, invest in existing and new projects, fund our ongoing business activities, and retire or service our outstanding debt could be significantly constrained.

Any downgrade in our credit ratings could limit our ability to obtain future financing, increase our future borrowing costs and adversely affect the market price of our existing securities, including the notes, or otherwise impair our business, financial condition and results of operations.

There can be no assurance that any rating assigned to any of our securities will remain in effect for any given period of time or that a rating will not be lowered, suspended or withdrawn entirely by a rating agency, if, in that rating agency’s judgment, circumstances so warrant. A downgrade of our credit ratings could adversely affect the market price of our securities, including the notes, result in an increase to our cost of financing, including with respect to the notes, limit our access to the capital or credit markets or otherwise adversely affect the availability of other new financing on favorable terms, result in more restrictive covenants in agreements governing the terms of any future indebtedness that we incur, increase our future cost of borrowing, or impair our business, financial condition and results of operations.

Current global financial conditions could adversely affect the availability of new financing and our operations.

Current global financial conditions have been characterized by increased market volatility. Continued volatility in the capital and credit markets, which impacts interest rates, currency exchange rates, and the availability of credit, could adversely affect our ability to obtain equity or debt financing in the future on terms favorable to us or have a material adverse effect on our business, financial condition and results of operations.

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USE OF PROCEEDS

We estimate that the net proceeds from this offering will be approximately $418.7 million, after deducting the underwriting discounts and commissions and estimated offering expenses payable by us. We intend to use up to approximately $300 million of the net proceeds from this offering to fund our pension liabilities and to implement pension derisking strategies, potentially including annuitizations. We intend to use any remaining net proceeds from this offering for liquidity and general corporate purposes.

Until the net proceeds from this offering are applied as described above, we may invest proceeds in short-term, investment grade interest-bearing securities or in obligations of, or guaranteed by, the U.S. government.

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CAPITALIZATION

The following table sets forth our consolidated capitalization as of June 30, 2023:

• on an actual basis; and

• on an as-adjusted basis to give effect to the offering of notes hereunder.

This table should be read in conjunction with our historical consolidated financial statements, including the related notes, which are incorporated by reference in this prospectus supplement and the accompanying prospectus, as well as any related free writing prospectus.

	As of June 30, 2023
	Actual			As Adjusted
	(Dollars in millions)
Cash and cash equivalents	$	267.1		$	685.8
Total debt (including current portion of long-term debt):
Revolving credit facility(1)		50.0			50.0
Term loan(2)		200.0			200.0
3.50% Convertible Senior Notes due 2025		291.4			291.4
4.875% Senior Notes due 2029		325.0			325.0
5.875% Senior Notes due 2027		350.0			350.0
7.250% Senior Notes due 2030 (offered hereby)		—			425.0
5.125% Senior Notes due 2031		350.0			350.0
Allegheny Ludlum 6.95% Debentures due 2025		150.0			150.0
Other debt(3)		72.9			72.9
Total debt		1,789.3			2,214.3
Stockholders’ equity:
Preferred stock, par value $0.10; 50,000,000 shares authorized; issued – none		—			—
Common stock, par value $0.10; 500,000,000 shares authorized; 132,268,866 shares issued; 128,584,727 shares outstanding		13.2			13.2
Additional paid-in-capital		1,682.0			1,682.0
Retained earnings		323.0			323.0
Treasury stock, at cost; 3,684,139 shares		(107.9	)		(107.9	)
Accumulated other comprehensive loss, net of tax		(716.3	)		(716.3	)
Total ATI stockholders’ equity		1,194.0			1,194.0
Noncontrolling interests		115.2			115.2
Total stockholders’ equity		1,309.2			1,309.2
Total ATI capitalization	$	3,098.5		$	3,523.5

(1) Our asset-based revolving credit facility provides for aggregate borrowings of up to $600 million. Borrowing availability under the facility is reduced on a dollar-for-dollar basis by the amount of any outstanding letters of credit under the facility. As of June 30, 2023, we had $50.0 million of outstanding borrowings under the facility, and approximately $39.4 million of letters of credit were outstanding under the facility. Our subsidiaries had the ability to borrow an additional approximately $500 million under our revolving credit facility as of June 30, 2023.

(2) Our term loan will mature on September 30, 2027.

(3) Excludes debt issuance costs.

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DESCRIPTION OF NOTES

The following description of the particular terms of the notes offered by this prospectus supplement supplements the description of the general terms and provisions of the debt securities set forth in the accompanying prospectus under the caption “Description of Debt Securities.”

In this Description of Notes, the terms “ATI,” the “Company,” “we,” “us” and similar words refer only to ATI Inc. and not to any of its subsidiaries.

The notes will be issued under a senior indenture dated as of September 14, 2021 (the “base indenture”), between us and Computershare Trust Company, N.A., as successor trustee to Wells Fargo Bank, National Association, as supplemented by a supplemental indenture to be dated as of August 11, 2023 (as so supplemented, the “senior indenture”). The senior indenture will be subject to and will be governed by the Trust Indenture Act of 1939, as amended. We have filed a form of the base indenture as an exhibit to the registration statement of which the accompanying prospectus forms a part and the executed base indenture as an exhibit to our most recent Annual Report on Form 10-K, which is incorporated by reference into this prospectus supplement and the accompanying prospectus. The following description summarizes selected provisions of the senior indenture and the notes. It does not restate the senior indenture or the terms of the notes in their entirety. We urge you to read the senior indenture and the notes because the senior indenture and the notes, and not this description, define the rights of noteholders.

General

The aggregate principal amount of the notes is $425,000,000. The notes will mature and become due and payable, together with any accrued and unpaid interest thereon, on August 15, 2030. The notes will bear interest at the rate of 7.250% per annum from August 11, 2023.

Interest on the notes will be payable semiannually in arrears on February 15 and August 15 of each year, beginning on February 15, 2024, to the persons in whose names the notes are registered at the close of business on the February 1 and August 1 preceding the respective interest payment dates (whether or not a business day). If any payment date is not a business day, then payment will be made on the next business day, but without any additional interest or other amount. Interest will be computed on the notes on the basis of a 360-day year of twelve 30-day months.

The notes will not be subject to any sinking fund.

The notes will be represented by one or more registered notes in global form, but in certain limited circumstances may be represented by notes in definitive form. See “— Book-Entry Issuance” in this prospectus supplement. The notes will be issued in U.S. dollars and only in minimum denominations of $2,000, and integral multiples of $1,000 in excess of $2,000.

The notes will constitute a series of debt securities to be issued under the senior indenture.

We will file annual statements with the trustee regarding our compliance with our obligations under the indenture governing the notes.

Ranking

The notes will be our senior and unsecured indebtedness and will rank equally with all of our other existing and future senior and unsecured indebtedness. The notes will effectively rank junior to any of our existing and future secured indebtedness to the extent of the assets securing such indebtedness, and will be structurally subordinated to any indebtedness and other liabilities of our subsidiaries. Indebtedness of our subsidiaries and obligations and liabilities of our subsidiaries are structurally senior to the notes since, in the event of a bankruptcy, liquidation, dissolution,

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reorganization or other winding up, the assets of our subsidiaries will be available to pay the notes only after the subsidiaries’ indebtedness and other obligations and liabilities are paid in full. If that happens, we may not have sufficient assets remaining to pay the amounts due on any or all of the notes then outstanding. Because we generally stand as an equity holder, rather than a creditor, of our subsidiaries, creditors of those subsidiaries will have their debt satisfied out of the subsidiaries’ assets before our creditors, including the noteholders.

As of June 30, 2023, we had an aggregate of approximately $1.7 billion of indebtedness outstanding, $250.0 million of which was secured. As of June 30, 2023, after giving effect to this offering, we would have had an aggregate of approximately $2.2 billion of indebtedness outstanding, $250.0 million of which would be secured. As of June 30, 2023, our subsidiaries had approximately $469 million of total indebtedness outstanding, principally comprised of the $200 million term loan outstanding under our existing senior secured credit facilities and $150 million in unsecured 6.95% Debentures due 2025 issued by our wholly owned subsidiary Allegheny Ludlum LLC and guaranteed by ATI. In addition, our subsidiaries had the ability to borrow an additional approximately $500 million under our revolving credit facility, which borrowings would be secured.

Additional Issuances

We may issue additional notes, without limitation and without your consent, provided that such additional notes must be part of the same issue as the notes offered hereby for United States federal income tax purposes. If we issue additional notes of the series offered by this prospectus supplement under the senior indenture, they will have the same terms and conditions as the notes being offered by this prospectus supplement in all respects (except for the payment of interest accruing prior to the issue date of the additional notes) so that the additional notes may be consolidated and form a single series with the notes offered by this prospectus supplement.

Optional Redemption

In addition to the provisions set forth below under “— Purchase of Notes upon a Change of Control Repurchase Event,” prior to August 15, 2026, we may redeem the notes at our option, at any time in whole or from time to time in part, at a redemption price equal to 100% of the principal amount of the notes plus the Applicable Premium as of, and accrued and unpaid interest to, but not including, the redemption date (subject to the right of holders of record on the relevant record date to receive interest due on the relevant interest payment date).

On and after August 15, 2026, we may redeem the notes at our option, at any time in whole or from time to time in part, at the redemption prices (expressed as percentages of principal amount of the notes to be redeemed) set forth below, plus accrued and unpaid interest to, but not including, the redemption date, on the principal amount of the notes to be redeemed to such redemption date, if redeemed during the twelve-month period beginning on or after August 15 of each of the years indicated below:

Year	Redemption Price
2026		103.625	%
2027		101.813	%
2028 and thereafter		100.000	%

In addition, at any time prior to August 15, 2026, we may, at our option and at any time or from time to time, redeem up to 40.0% of the aggregate principal amount of notes (calculated giving effect to any issuance of additional notes) at a redemption price equal to 107.250% of the aggregate

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principal amount thereof, plus accrued and unpaid interest to, but not including, the redemption date, on the principal amount of the notes to be redeemed to such redemption date, with the net proceeds of one or more Equity Offerings (within 180 days of the consummation of each such Equity Offering); provided that at least 60% of the original aggregate principal amount of notes (calculated giving effect to any issuance of additional notes) remain outstanding immediately after the occurrence of each such redemption.

The notes called for redemption become due on the date fixed for redemption. Notices of redemption will be mailed by first-class mail or sent electronically in accordance with DTC procedures at least 15 but not more than 60 days before the redemption date to each holder of notes to be redeemed at its registered address. The notice of redemption for the notes will state the amount to be redeemed. On and after the redemption date, interest will cease to accrue on any notes that are redeemed. If less than all of the notes are redeemed at any time, the trustee will select notes by such method as the trustee deems fair and appropriate, subject to applicable DTC procedures for global notes.

For purposes of determining the optional redemption price, the following definitions are applicable:

“Applicable Premium” means, with respect to the notes at the redemption date, the greater of (i) 1% of the principal amount of the notes and (ii) the excess (if any) of (A) the present value at the redemption date of (1) the redemption price of such note on August 15, 2026 (such redemption price being set forth in the second paragraph in this “— Optional Redemption” above) plus (2) all required remaining scheduled interest payments due on the notes through August 15, 2026 (but excluding accrued and unpaid interest to the redemption date), computed using a discount rate equal to the Treasury Rate plus 0.50% over (B) the principal amount of the notes outstanding on the redemption date. The trustee shall have no obligation to calculate or verify the calculation of the Applicable Premium or of any component thereof.

“Comparable Treasury Issue” means the United States Treasury security selected by an Independent Investment Banker as having a maturity comparable to the remaining term (the “Remaining Life”) of the notes to be redeemed that would be utilized, at the time of selection and in accordance with customary financial practice, in pricing new issues of corporate debt securities of comparable maturity to the remaining term of such notes.

“Comparable Treasury Price” means, with respect to any redemption date, the average of the Reference Treasury Dealer Quotations obtained by us for that redemption date, after excluding the highest and lowest of such Reference Treasury Dealer Quotations, or, if we are unable to obtain at least four such Reference Treasury Dealer Quotations, the average of all Reference Treasury Dealer Quotations obtained by us.

“Disqualified Stock” means, with respect to any Person, any capital stock of such Person which, by its terms, or by the terms of any security into which it is convertible or for which it is putable or exchangeable, or upon the happening of any event, matures or is mandatorily redeemable, other than as a result of a change of control or asset sale, pursuant to a sinking fund obligation or otherwise, or is redeemable at the option of the holder thereof, other than as a result of a change of control or asset sale, in whole or in part, in each case prior to the date 91 days after the earlier of the maturity date of the notes or the date the notes are no longer outstanding; provided that if such capital stock is issued pursuant to any plan for the benefit of employees of the Company or its Subsidiaries or by any such plan to such employees, such capital stock shall not constitute Disqualified Stock solely because it may be required to be repurchased by the Company or its Subsidiaries in order to satisfy applicable statutory or regulatory obligations.

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“Equity Offering” means any public or private sale of common shares or preferred shares of the Company (excluding Disqualified Stock), other than (a) public offerings with respect to the Company’s common shares registered on Form S-8 and (b) any sales to the Company or any of its Subsidiaries.

“Independent Investment Banker” means Citigroup Global Markets Inc., Goldman Sachs & Co. LLC and J.P. Morgan Securities LLC and their respective successors, as selected by us or, if such firms are unwilling or unable to select the applicable Comparable Treasury Issue or the applicable ratings scale for any Substitute Rating Agency, an independent investment banking institution of national standing appointed by us.

“Reference Treasury Dealer” means Citigroup Global Markets Inc. and its successors, and three other independent investment banking institutions of national standing appointed by us (each, a “Primary Treasury Dealer”); provided, however, that if any of the foregoing shall cease to be a Primary Treasury Dealer, we shall substitute therefor another Primary Treasury Dealer.

“Reference Treasury Dealer Quotations” means, with respect to each Reference Treasury Dealer and any redemption date for the notes to be redeemed, the average, as determined by us, of the bid and asked prices for the Comparable Treasury Issue, expressed in each case as a percentage of its principal amount, quoted in writing to the Independent Investment Banker by the Reference Treasury Dealer at 3:30 p.m., New York City time, on the third business day preceding the redemption date.

“Treasury Rate” means, with respect to any redemption date, (i) the yield, under the heading which represents the average for the immediately preceding week, appearing in the most recently published statistical release designated “Selected Interest Rates (Daily) – H.15” or any successor publication which is published weekly by the Board of Governors of the Federal Reserve System and which establishes yields on actively traded United States Treasury securities adjusted to constant maturity under the caption “Treasury Constant Maturities,” for the maturity corresponding to the Comparable Treasury Issue (if no maturity is within three months before or after the Remaining Life, yields for the two published maturities most closely corresponding to the Comparable Treasury Issue shall be determined and the Treasury Rate shall be interpolated or extrapolated from such yields on a straight-line basis, rounded to the nearest month) or (ii) if such release (or any successor release) is not published during the week preceding the calculation date or does not contain such yields, the rate per annum equal to the semiannual equivalent yield to maturity of the Comparable Treasury Issue, calculated using a price for the Comparable Treasury Issue (expressed as a percentage of its principal amount) equal to the Comparable Treasury Price for such redemption date. The Treasury Rate shall be calculated on the third business day preceding such redemption date.

The notes will not be entitled to the benefit of any sinking fund.

Purchase of Notes upon a Change of Control Repurchase Event

If a Change of Control Repurchase Event occurs, unless we have exercised our right to redeem the notes as described under the caption “— Optional Redemption,” we will be required to make an offer to each holder of the notes to repurchase all or any part (in minimum principal amounts of $2,000 and in integral multiples of $1,000 in excess thereof) of that holder’s notes at a repurchase price in cash equal to 101% of the aggregate principal amount of the notes repurchased plus any accrued and unpaid interest on the notes repurchased to, but not including, the date of repurchase. Within 30 days following any Change of Control Repurchase Event or, at our option, prior to any Change of Control, but after the public announcement of the Change of Control, we will mail or send a notice to each holder, with a copy to the trustee, describing the transaction or transactions that constitute or may constitute the Change of Control Repurchase Event and offering to repurchase the notes on the payment date specified in the notice, which date will be no earlier than 30 days and no later than

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60 days from the date such notice is mailed or sent. The notice shall, if mailed or sent prior to the date of consummation of the Change of Control, state that the offer to purchase is conditioned on a Change of Control Repurchase Event occurring on or prior to the payment date specified in the notice. We will comply with the requirements of Rule 14e-1 under the Exchange Act, and any other securities laws and regulations thereunder to the extent those laws and regulations are applicable in connection with the repurchase of the notes as a result of a Change of Control Repurchase Event. To the extent that the provisions of any securities laws or regulations conflict with the Change of Control Repurchase Event provisions of the notes, we will comply with the applicable securities laws and regulations and will not be deemed to have breached our obligations under the Change of Control Repurchase Event provisions of the notes by virtue of such conflict.

On the repurchase date following a Change of Control Repurchase Event, we will, to the extent lawful:

(1) accept for payment all the notes or portions of the notes properly tendered pursuant to our offer;

(2) deposit with the paying agent an amount equal to the aggregate purchase price in respect of all the notes or portions of the notes properly tendered; and

(3) deliver or cause to be delivered to the trustee the notes properly accepted, together with an officers’ certificate stating the aggregate principal amount of notes being purchased by the Company.

The paying agent will promptly deliver to each holder of notes properly tendered, the purchase price for the notes, and the trustee will promptly authenticate and mail (or cause to be transferred by book-entry) to each holder a new note equal in principal amount to any unpurchased portion of any notes surrendered.

We will not be required to make an offer to repurchase the notes upon a Change of Control Repurchase Event if a third party makes such an offer in the manner, at the times and otherwise in compliance with the requirements for an offer made by us and such third party purchases all notes properly tendered and not withdrawn under its offer.

The Change of Control Repurchase Event feature of the notes may in certain circumstances make more difficult or discourage a sale or takeover of ATI and, thus, the removal of incumbent management. The Change of Control Repurchase Event feature is a result of negotiations between us and the underwriters. We have no present intention to engage in a transaction involving a Change of Control, although it is possible that we could decide to do so in the future. As contemplated by the definition of Change of Control, we could enter into certain transactions, including acquisitions, refinancings or other recapitalizations that would not constitute a Change of Control under the senior indenture, but that could increase the amount of indebtedness outstanding at such time or otherwise affect our capital structure or the credit ratings of the notes. Restrictions on our ability to incur liens and enter into sale and leaseback transactions and on the ability of our domestic subsidiaries to guarantee our indebtedness are contained in the covenants described under the captions “— Covenants — Limitations on Liens,” “— Covenants — Limitations on Sale and Leaseback Transactions” and “— Covenants — Limitation on Guarantees.” Except for the limitations contained in such covenants and the covenant relating to repurchases upon the occurrence of a Change of Control Repurchase Event, the senior indenture will not contain any covenants or provisions that may afford holders of the notes protection in the event of a highly leveraged transaction.

We may not have sufficient funds to repurchase all the notes upon a Change of Control Repurchase Event. Even if we have sufficient funds, we may be prohibited from repurchasing the notes

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under the terms of our existing or future debt instruments. See “Risk Factors — Risks Relating to the Notes — We may not be able to repurchase the notes upon a change of control repurchase event.”

For purposes of the foregoing discussion of a repurchase at the option of holders, the following definitions are applicable:

“Change of Control” means the occurrence of any one of the following:

(1) the direct or indirect sale, lease, transfer, conveyance or other disposition (other than by way of merger or consolidation), in one or a series of related transactions, of all or substantially all of the assets of the Company and its Subsidiaries taken as a whole to any Person (including any “person” (as that term is used in Section 13(d)(3) of the Exchange Act)) other than to the Company or one of its Subsidiaries;

(2) the consummation of any transaction (including, without limitation, any merger or consolidation) the result of which is that any Person (including any “person” (as that term is used in Section 13(d)(3) of the Exchange Act)) becomes the “beneficial owner” (as defined in Rules 13d-3 and 13d-5 under the Exchange Act), directly or indirectly, of more than 50% of the outstanding Voting Stock of the Company, measured by voting power rather than number of shares;

(3) the Company consolidates with, or merges with or into, any Person, or any Person consolidates with, or merges with or into, the Company, in any such event pursuant to a transaction in which any of the outstanding Voting Stock of the Company or such other Person is converted into or exchanged for cash, securities or other property, other than any such transaction where the shares of the Voting Stock of the Company outstanding immediately prior to such transaction constitute, or are converted into or exchanged for, a majority of the Voting Stock of the surviving Person immediately after giving effect to such transaction; or

(4) the adoption of a plan relating to the liquidation or dissolution of the Company.

“Change of Control Repurchase Event” means the occurrence of both a Change of Control and a Ratings Event.

“Investment Grade” means a rating of Baa3 or better by Moody’s (or its equivalent under any successor Rating Categories of Moody’s), a rating of BBB- or better by S&P (or its equivalent under any successor Rating Categories of S&P) and the equivalent Investment Grade credit rating from any additional Rating Agency or Rating Agencies selected by the Company.

“Moody’s” means Moody’s Investors Service, Inc., and its successors.

“Person” means any individual, corporation, partnership, joint venture, association, joint-stock company, trust, unincorporated organization, limited liability company or government or other entity.

“Rating Agency” means (1) each of Moody’s and S&P and (2) if either of Moody’s or S&P ceases to rate the notes or fails to make a rating of the notes publicly available for reasons outside of the control of the Company, a Substitute Rating Agency thereof.

“Rating Category” means (i) with respect to S&P, any of the following categories: BBB, BB, B, CCC, CC, C and D (or equivalent successor categories); (ii) with respect to Moody’s, any of the following categories: Baa, Ba, B, Caa, Ca, C and D (or equivalent successor categories); and (iii) the equivalent of any such category of S&P or Moody’s used by another Rating Agency. In determining whether the rating of any notes has decreased by one or more gradations, gradations within Rating Categories (+ and — for S&P; 1, 2 and 3 for Moody’s; or the equivalent gradations for another Rating Agency) shall be taken into account (e.g., with respect to S&P, a decline in a rating from BB+ to BB, as well as from BB- to B+, will constitute a decrease of one gradation).

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“Rating Date” means the date that is 60 days prior to the earlier of (i) a Change of Control or (ii) public notice of the occurrence of a Change of Control or of the intention by the Company to effect a Change of Control.

“Ratings Event” means the occurrence of the events described in (a) or (b) of this definition on, or within 60 days after the earlier of, (i) the occurrence of a Change of Control or (ii) public notice of the occurrence of a Change of Control or the intention by the Company to effect a Change of Control (which period shall be extended so long as the rating of the notes is under publicly announced consideration for a possible downgrade by any of the Rating Agencies): (a) if the notes are rated by both Rating Agencies on the Rating Date as Investment Grade, the rating of the notes shall be reduced so that the notes are rated below Investment Grade by both Rating Agencies, or (b) if the notes are rated below Investment Grade by at least one Rating Agency, the ratings of the notes by both Rating Agencies shall be decreased by one or more gradations (including gradations within Rating Categories, as well as between Rating Categories) and the notes are then rated below Investment Grade by both Rating Agencies.

“S&P” means S&P Global Ratings, a division of S&P Global Inc., and its successors.

“Substitute Rating Agency” means a “nationally recognized statistical rating organization” within the meaning of Section 3(a)(62) of the Exchange Act, selected by the Company (as certified by a resolution of the board of directors of the Company) as a replacement agency for Moody’s or S&P, or both of them, as the case may be.

“Voting Stock” of any specified “person” (as that term is used in Section 13(d)(3) of the Exchange Act) as of any date means the capital stock of such person that is at the time entitled to vote generally in the election of the board of directors of such person.

Covenants

Except as described in “— Limitations on Liens,” “— Limitations on Sale and Leaseback Transactions” and “— Limitation on Guarantees,” neither we nor any of our subsidiaries will be restricted by the senior indenture from:

• incurring any indebtedness or other obligation;

• paying dividends or making distributions on our capital stock or the capital stock of any of our subsidiaries; or

• purchasing or redeeming our capital stock or the capital stock of any of our subsidiaries.

In addition, we will not be required to maintain any financial ratios or specified levels of net worth or liquidity or to repurchase or redeem or otherwise modify the terms of the notes upon a change of control or other events involving us or any of our subsidiaries which may adversely affect the creditworthiness of the notes, except to the limited extent described under the caption “— Purchase of Notes upon a Change of Control Repurchase Event.” Among other things, the senior indenture will not contain covenants designed to afford holders of the notes any protections in the event of a highly leveraged or other transaction involving us that may adversely affect holders of the notes, except to the limited extent described under the caption “— Purchase of Notes upon a Change of Control Repurchase Event.”

Limitations on Liens

We will not, and will not permit any of our Domestic Subsidiaries, directly or indirectly, to issue, assume or guarantee any Debt if that Debt is secured by any Lien upon any Principal Property (or portion thereof) of ours or of any Domestic Subsidiary or any shares of stock or Debt of any

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Domestic Subsidiary, whether owned on the date of the base indenture or thereafter acquired, without effectively securing the notes equally and ratably with that Debt, so long as such Debt is so secured. The foregoing restriction does not apply to:

(1) Liens on any property acquired, constructed or improved by us or any Domestic Subsidiary after the date of the base indenture, which are created or assumed contemporaneously with or within three years after its acquisition, or completion of construction or improvement (or within six months thereafter pursuant to a firm commitment for financing arrangements entered into within that three-year period) to secure or provide for the payment of the purchase price or cost thereof, or Liens existing on any property at the time of its acquisition;

(2) Liens existing on any property, shares of stock or indebtedness acquired from a Person merged with or into us or a Domestic Subsidiary after the date of the base indenture;

(3) with respect to any corporation that becomes a Domestic Subsidiary after the date of the base indenture, Liens on property of, or shares of stock or indebtedness issued by, any such corporation existing at the time it becomes a Domestic Subsidiary and not incurred in connection with or in anticipation of such corporation becoming a Domestic Subsidiary;

(4) Liens to secure Debt of a Domestic Subsidiary owed to us or Debt of one of our Domestic Subsidiaries owed to another Domestic Subsidiary;

(5) Liens in favor of governmental bodies to secure partial, progress, advance or other payments pursuant to any contract or statute;

(6) any Lien existing on the date of the base indenture; or

(7) Liens for the sole purpose of extending, renewing or replacing Debt, in whole or in part, secured by any Lien referred to in the foregoing clauses (1) to (6), inclusive, provided, however, that the principal amount of Debt secured by that Lien shall not exceed the principal amount of Debt so secured at the time of such extension, renewal or replacement, and that such extension, renewal or replacement shall be limited to the property that secured the Lien so extended, renewed or replaced (plus improvements on such property).

The limitation on liens described in this section shall not apply to the issuance, assumption or guarantee by us or any Domestic Subsidiary of Debt secured by a Lien which would otherwise be subject to the foregoing restrictions up to an aggregate amount which, together with all other Debt of ours and our Domestic Subsidiaries secured by Liens (not including Liens permitted under the foregoing exceptions) and the Attributable Debt with respect to Sale and Leaseback Transactions existing at that time (other than Sale and Leaseback Transactions in which the property involved would have been permitted to be subject to a Lien under clause (1) above), does not exceed 10% of Consolidated Net Tangible Assets.

Limitations on Sale and Leaseback Transactions

We and our Domestic Subsidiaries are prohibited from entering into Sale and Leaseback Transactions unless:

(a) we or such Domestic Subsidiary would be entitled to incur Debt secured by a Lien on the Principal Property to be leased without equally and ratably securing the notes, pursuant to clauses (1) to (7) under “— Limitations on Liens”; or the Attributable Debt with respect thereto would be an amount permitted under the last paragraph under “— Limitations on Liens”; or

(b) we or such Domestic Subsidiary shall, within 180 days of the effective date of any such arrangement apply an amount equal to the proceeds from such Sale and Leaseback Transaction to the

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payment or other retirement of Debt that ranks senior to or equal with the notes (other than, in either case, Debt owed by us or any Subsidiary) or to the purchase of other Principal Property.

Limitation on Guarantees

We and our Domestic Subsidiaries are prohibited from entering into any agreement pursuant to which any such Domestic Subsidiary guarantees the payment of Debt incurred by us without providing that the notes be equally and ratably guaranteed by such Domestic Subsidiary.

Certain Definitions

For purposes of “— Limitations on Liens,” “— Limitations on Sale and Leaseback Transactions” and “— Limitation on Guarantees,” the following definitions are applicable:

“Attributable Debt” in respect of a Sale and Leaseback Transaction means, as of any particular time, the present value (discounted at the rate of interest implicit in the terms of the lease involved in such Sale and Leaseback Transaction, as determined by us in good faith) of the obligation of the lessee thereunder for net rental payments (excluding, however, any amounts required to be paid by the lessee, whether or not designated as rent or additional rent, on account of maintenance and repairs, services, insurance, taxes, assessments, water rates or similar charges and any amounts required to be paid by the lessee thereunder contingent upon monetary inflation or the amount of sales, maintenance and repairs, insurance, taxes, assessments, water rates or similar charges) during the remaining term of that lease (including any period for which that lease has been extended or may, at the option of the lessor, be extended).

“Consolidated Net Tangible Assets” means the total of all the assets appearing on the consolidated balance sheet of the Company and its Subsidiaries, less the following: (A) current liabilities; (B) intangible assets such as goodwill, trademarks, trade names, patents and unamortized debt discount and expense; and (C) appropriate adjustments on account of minority interests of other Persons holding stock in any Subsidiary of the Company.

“Debt” means indebtedness for money borrowed.

“Domestic Subsidiary” means a Subsidiary formed under the laws of, or conducting its principal operations within, the United States or any State or territory thereof.

“Guarantee” means any obligation, contingent or otherwise, of any Person directly or indirectly guaranteeing any Debt or other obligation of any other Person and, without limiting the generality of the foregoing, any obligation, direct or indirect, contingent or otherwise, of such Person (i) to purchase or pay (or advance or supply funds for the purchase or payment of) such Debt or other obligation of such other Person (whether arising by virtue of partnership arrangements, or by agreement to keep-well, to purchase assets, goods, securities or services, to take-or-pay, or to maintain financial statement conditions or otherwise) or (ii) entered into for purposes of assuring in any other manner the obligee of such Debt or other obligation of the payment thereof or to protect such obligee against loss in respect thereof, in whole or in part; provided that the term “Guarantee” does not include endorsements for collection or deposit in the ordinary course of business. The term “Guarantee” used as a verb has a corresponding meaning.

“Lien” means any mortgage, pledge, lien, encumbrance, charge or security interest of any kind, excluding certain liens relating to taxes, easements and similar liens arising in the ordinary course of business.

“Principal Property” means any manufacturing plant or other similar facility owned by the Company or any Domestic Subsidiary, the book value of the real property, plant and equipment of

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which (as shown, without deduction of any depreciation reserves, on the books of the owner or owners) is not less than two percent (2%) of Consolidated Net Tangible Assets except (A) any such plant or facility which our Board of Directors determines is not of material importance to the total business conducted, or assets owned, by the Company and its Domestic Subsidiaries as an entirety or (B) any portion of any such plant or facility which our Board of Directors determines not to be of material importance to the use or operation thereof.

“Sale and Leaseback Transaction” means any arrangement with any Person providing for the leasing to the Company or any Domestic Subsidiary of any Principal Property or portion thereof (except for temporary leases for a term, including any renewal thereof, of not more than 36 months and except for leases between the Company and a Subsidiary or between Subsidiaries), which Principal Property (or portion thereof) has been or is to be sold or transferred by the Company or such Domestic Subsidiary to such Person.

“Subsidiary” means with respect to any Person, any corporation, association or other business entity of which more than 50% of the outstanding voting stock is owned, directly or indirectly, by such Person and one or more Subsidiaries of such Person (or combination thereof). Unless otherwise specified, “Subsidiary” means a Subsidiary of the Company.

Merger, Consolidation or Sale of Assets

We are generally permitted under the senior indenture to merge or consolidate with another corporation or other entity. We also are permitted under the senior indenture to sell all or substantially all of our assets to another corporation or other entity. We may not take any of these actions unless all the following conditions, among other things, are met:

• If the successor entity in the transaction is not the Company, the successor entity must be organized as a corporation, limited liability company, partnership or trust and must expressly assume by supplemental indenture our obligations under the debt securities of each series issued under the base indenture and the indenture with respect to that series. The successor entity must be organized under the laws of the United States, any State thereof or the District of Columbia.

• Immediately after the transaction, no default under the debt securities issued under the base indenture has occurred and is continuing. For this purpose, “default under the debt securities issued under the base indenture” means an event of default with respect to a series of such debt securities, including the notes, or any event that would be an event of default with respect to a series of such debt securities, including the notes, if the requirements for giving us default notice and for our default having to continue for a specific period of time were disregarded.

If the conditions described above are satisfied with respect to the debt securities of any series of debt securities issued under the base indenture, including the notes, we will not need to obtain the approval of the holders of those debt securities in order to merge or consolidate or to sell all or substantially all our assets. Also, these conditions will apply only if we wish to merge or consolidate with another entity or sell all or substantially all of our assets to another entity. We will not need to satisfy these conditions if we enter into other types of transactions, including any transaction in which we acquire the stock or assets of another entity, any transaction that involves a change of control of the Company but in which we do not merge or consolidate and any transaction in which we sell less than substantially all our assets.

The successor entity will be substituted for the Company with respect to the debt securities of any series issued under the base indenture, including the notes, and under the base indenture with the

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same effect as if it had been an original party to the base indenture, and, except in the case of a lease, the Company will be relieved from any further obligations and covenants under the base indenture.

Events of Default

The events of default with respect to the notes will be those events described under the caption “Description of Debt Securities — Default, Remedies and Waiver of Default — Events of Default” in the accompanying prospectus, except that each of the following will also be events of default:

• a failure by the Company to repurchase notes tendered for repurchase following the occurrence of a Change of Control Repurchase Event in conformity with the covenant described under the caption “— Purchase of Notes upon a Change of Control Repurchase Event”; and

• a failure by the Company or any of its Subsidiaries to pay any Debt, within any applicable grace period after final maturity or the acceleration by the holders thereof, if the total amount of such Debt unpaid or accelerated exceeds $125 million.

For a description of the remedies available to holders of the notes as a result of an event of default, see “Description of Debt Securities — Default, Remedies and Waiver of Default — Remedies if an Event of Default Occurs” in the accompanying prospectus.

Modification and Waivers

The base indenture contains provisions permitting us and the trustee to enter into one or more supplemental indentures without the consent of the holders of debt securities issued thereunder, including the notes, for any of the following purposes:

• to evidence the succession of another entity to us in accordance with “— Merger, Consolidation or Sale of Assets”;

• to add to our covenants further covenants for the benefit or protection of the holders of any or all series of debt securities issued thereunder, or to surrender any right or power conferred upon us by the base indenture;

• to add any additional events of default with respect to all or any series of debt securities issued thereunder;

• to add to or change any of the provisions of the base indenture or any supplemental indenture to facilitate the issuance of debt securities in bearer form with or without coupons, or to permit or facilitate the issuance of debt securities in uncertificated form;

• to add to, change or eliminate any of the provisions of the base indenture or any supplemental indenture in respect of one or more series of debt securities issued thereunder, under certain conditions designed to protect the rights of any existing holder of those debt securities;

• to secure all or any series of debt securities issued thereunder;

• to establish the forms or terms of the debt securities of any new series issued thereunder;

• to evidence the appointment of a successor trustee and to add to or change provisions of the base indenture necessary to provide for or facilitate the administration of the trusts under the base indenture by more than one trustee;

• to add to or change any provisions of the base indenture with respect to any debt securities issued thereunder that are convertible into securities or other property other than debt

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securities of the same series and of like tenor, in order to permit or facilitate the issuance, payment or conversion of such debt securities;

• to conform the text of the base indenture or any supplemental indenture or any debt securities issued thereunder to any provision of a relevant offering document to the extent such provision was intended to be a verbatim recitation of a provision of the base indenture, any supplemental indenture or such debt securities; or

• to cure any ambiguity, to correct or supplement any provision of the base indenture which may be defective or inconsistent with another provision of the base indenture or to make any other provisions with respect to matters or questions arising under the base indenture or any supplemental indenture, provided that any such action shall not adversely affect the interests of the holders of any series of debt securities issued thereunder.

We and the trustee may otherwise modify the base indenture or any supplemental indenture with the consent of the holders of not less than a majority in aggregate principal amount of each series of debt securities affected thereby at the time outstanding, except that no such modifications shall, without the consent of the holder of each outstanding debt security affected thereby:

• change the fixed maturity of the principal of any such debt securities or any installment of principal or interest on any such debt securities, reduce the principal amount thereof or the rate of interest or premium payable upon redemption, reduce the amount of principal of an original issue discount debt security or any other debt security that would be due and payable upon a declaration of acceleration of the maturity thereof, permit us to redeem any such debt securities if we otherwise would not be permitted to do so, change the place of payment where or change the currency in which any such debt securities are payable or impair the right to institute suit for the enforcement of any such payment after the stated maturity thereof or the redemption date, if applicable;

• impair the rights of any holder of such debt securities to require repurchase or conversion of such debt securities on the terms provided therein if any such debt securities provide that the holders thereof may require us to repurchase or convert such debt securities;

• reduce the percentage in principal amount of debt securities of any series, the consent of the holders of which is required for any waiver or supplemental indenture; or

• modify the provisions of the base indenture relating to the waiver of past defaults or the waiver or certain covenants or the provisions described above, except to increase any percentage set forth in those provisions or to provide that other provisions of the base indenture may not be modified without the consent of the holder of each debt security affected thereby.

With respect to any vote of holders of a series of debt securities, we generally will be entitled to set any date as a record date for the purpose of determining the holders of outstanding debt securities that are entitled to vote or take other action under the base indenture.

Satisfaction and Discharge; Defeasance and Covenant Defeasance

The provisions of the senior indenture described under the caption “Description of Debt Securities — Defeasance, Covenant Defeasance and Satisfaction and Discharge” in the accompanying prospectus will be applicable to the notes.

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Exchange and Transfer

You may exchange or transfer the notes in accordance with the senior indenture. You will not be required to pay a service charge to exchange or transfer the notes, but you may be required to pay for any tax or other governmental charge associated with the exchange or transfer. The transferor of any note shall provide or cause to be provided to the trustee all information necessary to allow the trustee to comply with any applicable tax reporting obligations, including without limitation any cost basis reporting obligations under Internal Revenue Code Section 6045. The trustee may rely on information provided to it and shall have no responsibility to verify or ensure the accuracy of such information. The exchange or transfer will only be made if the transfer agent is satisfied with your proof of ownership. See “— Book-Entry Issuance.”

Trustee and Paying Agent

Computershare Trust Company, N.A., as successor to Wells Fargo Bank, National Association, will act as trustee under the senior indenture and as our paying agent for the notes. We may choose to pay interest by mailing checks or making wire or other electronic funds transfers. Regardless of who acts as the paying agent, and subject to applicable abandoned property laws, all money paid by us to a paying agent that remains unclaimed at the end of two years after the amount is due to note holders will be repaid to us. After that two-year period, you may look only to us for payment and not to the trustee, any other paying agent or anyone else. We may also arrange for additional payment offices, and may cancel or change these offices, including any use of the trustee’s corporate trust office. We may appoint or change any paying agent without prior notice to any note holder.

The trustee (including in its capacity as paying agent), assumes no responsibility and will have no liability for the accuracy, correctness, adequacy or completeness of the information concerning us or our affiliates or any other party contained in this document or the related documents or for any failure by us or any other party to disclose events that may have occurred and may affect the significance or accuracy of such information. The trustee will be permitted to engage in other transactions with us; however, if it acquires any conflicting interest as defined in the Trust Indenture Act it must eliminate such conflict within 90 days, apply to the SEC for permission to continue or resign. The trustee shall not be responsible for determining whether any Change of Control has occurred and whether any Change of Control Offer with respect to the notes is required. The trustee shall not be responsible for monitoring our rating status, making any request upon any Rating Agency, or determining whether any Ratings Event has occurred.

Governing Law

The laws of the State of New York will govern the senior indenture and the notes.

Book-Entry Issuance

We have obtained the information in this section concerning DTC, Clearstream Banking S.A., or “Clearstream,” and Euroclear Bank SA/NV, as operator of the Euroclear System, or “Euroclear,” and the book-entry system and procedures from sources that we believe to be reliable, but we take no responsibility for the accuracy of this information.

The notes will be issued as fully-registered global notes which will be deposited with, or on behalf of, DTC and registered, at the request of DTC, in the name of Cede & Co. Beneficial interests in the global notes will be represented through book-entry accounts of financial institutions acting on behalf of beneficial owners as direct or indirect participants in DTC. Investors may elect to hold their interests in the global notes through either DTC (in the United States) or (in Europe) through

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Clearstream or through Euroclear. Investors may hold their interests in the global notes directly if they are participants of such systems, or indirectly through organizations that are participants in these systems. Interests held through Clearstream and Euroclear will be recorded on DTC’s books as being held by the U.S. depositary for each of Clearstream and Euroclear (the “U.S. Depositaries”), which U.S. Depositaries will, in turn, hold interests on behalf of their participants’ customers’ securities accounts. Beneficial interests in the global notes will be held in denominations of $2,000 and integral multiples of $1,000 in excess thereof. Except as set forth below, the global notes may be transferred, in whole and not in part, only to another nominee of DTC or to a successor of DTC or its nominee.

Notes represented by a global note can be exchanged for definitive securities in registered form only if:

• DTC notifies us that it is unwilling or unable to continue as depositary for that global note and we do not appoint a successor depositary within 90 days after receiving that notice;

• at any time DTC ceases to be a clearing agency registered under the Exchange Act and we do not appoint a successor depositary within 90 days after becoming aware that DTC has ceased to be registered as a clearing agency;

• we, in our sole discretion, determine that that global note will be exchangeable for definitive securities in registered form and notify the trustee of our decision; or

• an event of default with respect to the notes represented by that global note has occurred and is continuing.

A global note that can be exchanged as described in the preceding sentence will be exchanged for definitive securities issued in authorized denominations in registered form for the same aggregate amount. The definitive securities will be registered in the names of the owners of the beneficial interests in the global note as directed by DTC. In connection with any proposed exchange of a global note for a definitive note, there shall be provided to the trustee all information necessary to allow the trustee to comply with any applicable tax reporting obligations, including without limitation any cost basis reporting obligations under Internal Revenue Code Section 6045. The trustee may rely on information provided to it and shall have no responsibility to verify or ensure the accuracy of such information.

We will make principal and interest payments on all notes represented by a global note to the paying agent which in turn will make payment to DTC or its nominee, as the case may be, as the sole registered owner and the sole holder of the notes represented by such global note for all purposes under the senior indenture.

Accordingly, we, the trustee and any paying agent will have no responsibility or liability for:

• any aspect of DTC’s records relating to, or payments made on account of, beneficial ownership interests in a debt security represented by a global note;

• any other aspect of the relationship between DTC and its participants or the relationship between those participants and the owners of beneficial interests in a global note held through those participants;

• the maintenance, supervision or review of any of DTC’s records relating to those beneficial ownership interests; or

• any operations or procedures of DTC, or for any act or omission by DTC.

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DTC has advised us that its current practice is to credit participants’ accounts on each payment date with payments in amounts proportionate to their respective beneficial interests in the principal amount of such global note as shown on DTC’s records, upon DTC’s receipt of funds and corresponding detail information. The underwriters will initially designate the accounts to be credited. Payments by participants to owners of beneficial interests in a global note will be governed by standing instructions and customary practices, as is the case with securities held for customer accounts registered in “street name,” and will be the sole responsibility of those participants. Book-entry notes may be more difficult to pledge because of the lack of a physical note.

DTC

So long as DTC or its nominee is the registered owner of a global note, DTC or its nominee, as the case may be, will be considered the sole owner and holder of the notes represented by that global note for all purposes of the notes. Owners of beneficial interests in the notes will not be entitled to have notes registered in their names, will not receive or be entitled to receive notices or physical delivery of the notes in definitive form and will not be considered owners or holders of notes under the senior indenture. Accordingly, each person owning a beneficial interest in a global note must rely on the procedures of DTC and, if that person is not a DTC participant, on the procedures of the participant through which that person owns its interest, to exercise any rights of a holder of notes. The laws of some jurisdictions require that certain purchasers of securities take physical delivery of the securities in certificated form. These laws may impair the ability to transfer beneficial interests in a global note. Beneficial owners may experience delays in receiving distributions on their notes since distributions will initially be made to DTC and must then be transferred through the chain of intermediaries to the beneficial owner’s account.

We understand that, under existing industry practices, if we request holders to take any action, or if an owner of a beneficial interest in a global note desires to take any action which a holder is entitled to take under the senior indenture, then DTC would authorize the participants holding the relevant beneficial interests to take that action and those participants would authorize the beneficial owners owning through such participants to take that action or would otherwise act upon the instructions of beneficial owners owning through them.

Beneficial interests in a global note will be shown on, and transfers of those ownership interests will be effected only through, records maintained by DTC and its participants for that global note. The conveyance of notices and other communications by DTC to its participants and by its participants to owners of beneficial interests in the notes will be governed by arrangements among them, subject to any statutory or regulatory requirements in effect.

DTC has advised us that it is a limited-purpose trust company organized under the New York banking law, a “banking organization” within the meaning of the New York banking law, a member of the Federal Reserve System, a “clearing corporation” within the meaning of the New York Uniform Commercial Code and a “clearing agency” registered under the Exchange Act.

DTC holds the securities of its participants and facilitates the clearance and settlement of securities transactions among its participants in such securities through electronic book-entry changes in accounts of its participants. The electronic book-entry system eliminates the need for physical certificates. DTC’s participants include securities brokers and dealers (including the underwriters), banks, trust companies, clearing corporations and certain other organizations, some of which, and/or their representatives, own DTC. Banks, brokers, dealers, trust companies and others that clear through or maintain a custodial relationship with a participant, either directly or indirectly, also have access to DTC’s book-entry system. The rules applicable to DTC and its participants are on file with the SEC.

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DTC has advised us that the above information with respect to DTC has been provided to its participants and other members of the financial community for informational purposes only and is not intended to serve as a representation, warranty or contract modification of any kind.

Clearstream

Clearstream has advised us that it is incorporated under the laws of Luxembourg as a professional depositary.

Clearstream holds securities for its participating organizations, or “Clearstream Participants,” and facilitates the clearance and settlement of securities transactions between Clearstream Participants through electronic book-entry changes in accounts of Clearstream Participants, thereby eliminating the need for physical movement of certificates. Clearstream provides to Clearstream Participants, among other things, services for safekeeping, administration, clearance and settlement of internationally traded securities and securities lending and borrowing. Clearstream interfaces with domestic securities markets in several countries. As a professional depositary, Clearstream is subject to regulation by the Luxembourg Commission for the Supervision of the Financial Sector (Commission de Surveillance du Secteur Financier). Clearstream Participants are recognized financial institutions around the world, including underwriters, securities brokers and dealers, banks, trust companies, clearing corporations and certain other organizations. Clearstream’s U.S. Participants are limited to securities brokers and dealers and banks. Indirect access to Clearstream is also available to others, such as banks, brokers, dealers and trust companies that clear through or maintain a custodial relationship with a Clearstream Participant either directly or indirectly.

Distributions with respect to notes held beneficially through Clearstream will be credited to cash accounts of Clearstream Participants in accordance with its rules and procedures, to the extent received by the U.S. Depositary for Clearstream.

Euroclear

Euroclear has advised us that it was created in 1968 to hold securities for participants of Euroclear, or “Euroclear Participants,” and to clear and settle transactions between Euroclear Participants through simultaneous electronic book-entry delivery against payment, thereby eliminating the need for physical movement of certificates and any risk from lack of simultaneous transfers of securities and cash. Euroclear performs various other services, including securities lending and borrowing and interacts with domestic markets in several countries. Euroclear is operated by Euroclear Bank S.A./N.V., or the “Euroclear Operator,” under contract with Euroclear plc, a U.K. corporation. All operations are conducted by the Euroclear Operator, and all Euroclear securities clearance accounts and Euroclear cash accounts are accounts with the Euroclear Operator, not Euroclear plc. Euroclear plc establishes policy for Euroclear on behalf of Euroclear Participants. Euroclear Participants include banks, including central banks, securities brokers and dealers and other professional financial intermediaries. Indirect access to Euroclear is also available to other firms that clear through or maintain a custodial relationship with a Euroclear Participant, either directly or indirectly.

The Euroclear Operator is a Belgian bank. As such it is regulated by the Belgian Banking and Finance Commission.

Securities clearance accounts and cash accounts with the Euroclear Operator are governed by the Terms and Conditions Governing Use of Euroclear and the related Operating Procedures of the Euroclear System, and applicable Belgian law, which we will refer to herein as the “Terms and Conditions.” The Terms and Conditions govern transfers of securities and cash within Euroclear, withdrawals of securities and cash from Euroclear, and receipts of payments with respect to securities

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in Euroclear. All securities in Euroclear are held on a fungible basis without attribution of specific certificates to specific securities clearance accounts. The Euroclear Operator acts under the Terms and Conditions only on behalf of Euroclear Participants, and has no record of or relationship with persons holding through Euroclear Participants.

Distributions with respect to notes held beneficially through Euroclear will be credited to the cash accounts of Euroclear Participants in accordance with the Terms and Conditions, to the extent received by the U.S. Depositary for Euroclear.

Euroclear has further advised us that investors that acquire, hold and transfer interests in the notes by book-entry through accounts with the Euroclear Operator or any other securities intermediary are subject to the laws and contractual provisions governing their relationship with their intermediary, as well as the laws and contractual provisions governing the relationship between such an intermediary and each other intermediary, if any, standing between themselves and the global notes.

Global Clearance and Settlement Procedures

Initial settlement for the notes will be made in immediately available funds. Secondary market trading between DTC participants will occur in the ordinary way in accordance with DTC rules and will be settled in immediately available funds using DTC’s Same-Day Funds Settlement System. Secondary market trading between Clearstream Participants and/or Euroclear Participants will occur in the ordinary way in accordance with the applicable rules and operating procedures of Clearstream and Euroclear and will be settled using the procedures applicable to conventional eurobonds in immediately available funds.

Cross-market transfers between persons holding directly or indirectly through DTC, on the one hand, and directly or indirectly through Clearstream Participants or Euroclear Participants, on the other, will be effected through DTC in accordance with DTC rules on behalf of the relevant European international clearing system by its U.S. Depositary; however, such cross-market transactions will require delivery of instructions to the relevant European international clearing system by the counterparty in such system in accordance with its rules and procedures and within its established deadlines (European time). The relevant European international clearing system will, if the transaction meets its settlement requirements, deliver instructions to its U.S. Depositary to take action to effect final settlement on its behalf by delivering or receiving notes through DTC, and making or receiving payment in accordance with normal procedures for same-day funds settlement applicable to DTC. Clearstream Participants and Euroclear Participants may not deliver instructions directly to their respective U.S. Depositaries.

Because of time-zone differences, credits of notes received through Clearstream or Euroclear as a result of a transaction with a DTC participant will be made during subsequent securities settlement processing and dated the business day following the DTC settlement date. Such credits or any transactions in such notes settled during such processing will be reported to the relevant Euroclear Participants or Clearstream Participants on such business day. Cash received in Clearstream or Euroclear as a result of sales of notes by or through a Clearstream Participant or a Euroclear Participant to a DTC participant will be received with value on the DTC settlement date but will be available in the relevant Clearstream or Euroclear cash account only as of the business day following settlement in DTC.

If the notes are cleared only through Euroclear and Clearstream (and not DTC), you will be able to make and receive through Euroclear and Clearstream payments, deliveries, transfers, exchanges, notices and other transactions involving any securities held through those systems only on days when those systems are open for business. Those systems may not be open for business on days

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when banks, brokers and other institutions are open for business in the United States. In addition, because of time-zone differences, U.S. investors who hold their interests in the securities through these systems and wish to transfer their interests, or to receive or make a payment or delivery or exercise any other right with respect to their interests, on a particular day may find that the transaction will not be effected until the next business day in Luxembourg or Brussels, as applicable. Thus, U.S. investors who wish to exercise rights that expire on a particular day may need to act before the expiration date.

Although DTC, Clearstream and Euroclear have agreed to the foregoing procedures in order to facilitate transfers of notes among participants of DTC, Clearstream and Euroclear, they are under no obligation to perform or continue to perform such procedures and such procedures may be modified or discontinued at any time. None of us, the trustee nor any paying agent will have any responsibility for the performance by or for any act or omission of DTC, Euroclear or Clearstream or their respective direct or indirect participants of their obligations under the rules and procedures governing their operations.

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MATERIAL U.S. FEDERAL INCOME TAX CONSIDERATIONS

This section is a summary of certain material U.S. federal income tax considerations relating to the ownership and disposition of the notes. This summary does not provide a complete analysis of all potential tax considerations. The information provided below is based on existing U.S. federal income tax authorities, all of which are subject to change or differing interpretations, possibly with retroactive effect. There can be no assurance that the Internal Revenue Service (the “IRS”) will not challenge one or more of the tax consequences described herein, and we have not obtained, and do not intend to obtain, a ruling from the IRS with respect to the U.S. federal income tax consequences of owning or disposing of the notes. The summary generally applies only to beneficial owners of the notes that purchase their notes in this offering for an amount equal to the “issue price” of the notes, which is the first price at which a substantial amount of the notes is sold for money to the public (not including sales to bond houses, brokers or similar persons or organizations acting in the capacity of underwriters, initial purchasers, placement agents or wholesalers), and that hold the notes as “capital assets” (generally, for investment). This discussion does not purport to deal with all aspects of U.S. federal income taxation that may be relevant to a particular beneficial owner in light of the beneficial owner’s circumstances (for example, persons subject to the alternative minimum tax provisions of the U.S. Internal Revenue Code of 1986, as amended (the “Code”), or a U.S. holder (as defined below) whose “functional currency” is not the U.S. dollar). Also, it is not intended to be wholly applicable to all categories of investors, some of which may be subject to special rules (such as an S corporation or other pass-through entity (or an investor in an S corporation or other pass-through entity), dealers in securities, traders in securities that elect to use a mark-to-market method of accounting, accrual-method taxpayers subject to section 451(b) of the Code, banks, thrifts, regulated investment companies, real estate investment trusts, insurance companies, tax-exempt entities, tax-deferred or other retirement accounts, certain former citizens or residents of the United States, persons holding notes as part of a straddle, persons purchasing or selling notes as part of a wash sale for U.S. federal income tax purposes, entities treated as “controlled foreign corporations” or “passive foreign investment companies” for U.S. federal income tax purposes, or persons deemed to sell notes under the constructive sale provisions of the Code). Finally, the summary does not address the potential application of the Medicare tax on net investment income, the effects of the U.S. federal estate and gift tax laws or the effects of any applicable non-U.S. laws or U.S. state or local laws, or subsequent purchases of the notes.

INVESTORS CONSIDERING THE PURCHASE OF NOTES SHOULD CONSULT THEIR OWN TAX ADVISORS REGARDING THE APPLICATION OF U.S. FEDERAL INCOME, ESTATE OR GIFT TAX LAWS, NON-U.S. LAWS, U.S. STATE AND LOCAL LAWS, AND TAX TREATIES TO THEIR PARTICULAR SITUATIONS.

As used herein, the term “U.S. holder” means a beneficial owner of notes that, for U.S. federal income tax purposes, is (1) a citizen or individual resident of the United States, (2) a corporation (or other entity treated as a corporation for U.S. federal income tax purposes) created or organized in or under the laws of the United States or any state of the United States, or the District of Columbia, (3) an estate the income of which is subject to U.S. federal income taxation regardless of its source, or (4) a trust if it (x) is subject to the primary supervision of a U.S. court and the control of one of more U.S. persons or (y) has a valid election in effect under applicable U.S. Treasury regulations to be treated as a U.S. person.

A “non-U.S. holder” is a beneficial owner of notes (other than a partnership, S corporation, grantor trust or other pass-through or disregarded entity for U.S. federal income tax purposes) that is not a U.S. holder.

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If a partnership (or other entity or arrangement treated as a partnership) for U.S. federal income tax purposes is a beneficial owner of a note, the tax treatment of a partner in the partnership will depend upon the status of the partner and the activities of the partnership. A beneficial owner of notes that is a partnership, and partners in such a partnership, should consult his, her or its tax advisor about the U.S. federal income tax consequences of owning and disposing of the notes.

U.S. Holders

The following discussion is limited to the U.S. federal income tax consequences relevant to a U.S. holder (as defined above).

Certain Additional Payments

Under the terms of the notes, there are circumstances in which we might be required to make payments on a note that would increase the yield of the note, as described under “Description of the Notes — Purchase of Notes upon a Change of Control Repurchase Event.” Under U.S. Treasury regulations, the possibility of such excess amounts being paid will not affect the amount of interest income a holder recognizes, in advance of the payment of such excess amounts, if there is only a remote possibility as of the date the notes were issued that the holder would receive such amounts. We believe that there is only a remote possibility that we would be required to make such payments, and therefore we do not intend to treat the notes as subject to the special rules governing “contingent payment debt instruments.” Our position that the notes are not subject to these special rules is binding on a holder unless the holder discloses a contrary position in the manner required by applicable U.S. Treasury regulations. If the IRS takes a contrary position, a U.S. holder may be required to accrue interest income based upon a “comparable yield” (as defined in the U.S. Treasury regulations) determined at the time of issuance of the notes (which is not expected to differ significantly from the actual yield on the notes), with adjustments to such accruals when any contingent payments are made that differ from the payments based on the comparable yield. In addition, any income on the sale, exchange, redemption or other taxable disposition of the notes would be treated as interest income rather than as capital gain. U.S. holders should consult their tax advisors regarding the tax consequences if the notes were treated as contingent payment debt instruments. The remainder of this discussion assumes that the notes are not treated as contingent payment debt instruments.

Payments of Interest

A U.S. holder will be required to recognize as ordinary income any stated interest paid or accrued on the notes, in accordance with its regular method of tax accounting.

In general, if the stated principal amount of a debt instrument exceeds its issue price by at least a statutorily defined de minimis amount, a U.S. holder will be required to include such excess in income as “original issue discount” over the term of the instrument in accordance with a constant-yield method, irrespective of the holder’s regular method of tax accounting. Generally, original issue discount is considered to be de minimis if it is less than 0.25% of the instrument’s stated principal amount multiplied by the number of complete years from the issue date to maturity. We anticipate, and therefore this discussion assumes, that the notes will not be issued with original issue discount for U.S. federal income tax purposes.

Sale, Exchange, Redemption or Other Taxable Disposition of Notes

A U.S. holder generally will recognize capital gain or loss if it disposes of a note in a sale, exchange, redemption or other taxable disposition. The U.S. holder’s gain or loss generally will equal the difference between the amount realized by it (other than amounts attributable to accrued but unpaid

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interest) and its tax basis in the note. The U.S. holder’s tax basis in the note generally will equal the amount it paid for the note. The portion of any amount realized that is attributable to accrued interest will not be taken into account in computing the U.S. holder’s capital gain or loss. Instead, that portion will be recognized as ordinary interest income to the extent that the U.S. holder has not previously included the accrued interest in income. The gain or loss recognized by the U.S. holder on the disposition of the note will be long-term capital gain or loss if it has held the note for more than one year, or short-term capital gain or loss if it has held the note for one year or less, at the time of the disposition. Long-term capital gains of non-corporate taxpayers currently are taxed at preferential rates. Short-term capital gains currently are taxed at ordinary income rates. The deductibility of capital losses is subject to limitations.

Non-U.S. Holders

The following discussion is limited to the U.S. federal income tax consequences relevant to a non-U.S. holder (as defined above). This summary does not discuss all of the tax consequences that may be relevant to certain holders in light of their particular circumstances or to holders subject to special rules (as described above in the initial paragraph of this summary), including certain nonresident alien individuals who have lost their U.S. citizenship or who ceased to be treated as resident aliens of the United States, corporations that are treated as domestic personal holding companies, controlled foreign corporations, or passive foreign investment companies and non-U.S. holders that are owned or controlled by U.S. holders. Investors considering the purchase of notes should consult their tax advisor about the application of U.S. federal income, estate and gift tax laws to their particular situations, as well as any tax consequences arising under the laws of any state, local or non-U.S. tax jurisdiction or under an applicable tax treaty.

Payments of Interest

Subject to the discussions below regarding the Foreign Account Tax Compliance Act (“FATCA”) and under “— Income or Gains Effectively Connected with a U.S. Trade or Business,” payments of interest on the notes to non-U.S. holders will generally qualify as “portfolio interest,” and thus will be exempt from U.S. federal income tax, including withholding of such tax, if the non-U.S. holder certifies its non-U.S. status as described below.

The portfolio interest exemption will not apply to payments of interest to a non-U.S. holder that:

• owns, actually or constructively, shares of our stock representing at least 10% of the total combined voting power of all classes of our stock entitled to vote;

• is a bank whose receipt of interest is described in section 881(c)(3)(A) of the Code; or

• is a “controlled foreign corporation” that is related, directly or indirectly, to us through sufficient actual or constructive stock ownership.

The portfolio interest exemption applies only if the non-U.S. holder certifies its non-U.S. status. A non-U.S. holder can meet this certification requirement by providing a properly completed and executed IRS Form W-8BEN or W-8BEN-E or appropriate substitute form prior to the payment. If the non-U.S. holder holds the note through a financial institution or other agent acting on its behalf, it will be required to provide appropriate documentation to the agent.

Special certification rules apply to non-U.S. holders that are pass-through or disregarded entities.

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If the portfolio interest exemption does not apply to payments of interest to a non-U.S. holder, and subject to the discussion below under “—Income or Gains Effectively Connected with a U.S. Trade or Business,” these payments will be subject to U.S. federal withholding tax at a rate of 30% (or a lower treaty rate if the non-U.S. holder is eligible for the benefits of a tax treaty between the United States and its country of residence and provides appropriate certification of eligibility to the applicable withholding agent).

Sale, Exchange, Redemption or Other Taxable Disposition of Notes

Subject to the discussion below regarding backup withholding, non-U.S. holders generally will not be subject to U.S. federal income or withholding tax on any gain realized on the sale, exchange, redemption or other taxable disposition of notes (other than with respect to payments attributable to accrued interest, which will be taxed as described under “— Payments of Interest” above) unless:

• the gain is effectively connected with the conduct by the non-U.S. holder of a U.S. trade or business (and, generally, if required by an applicable income tax treaty, is attributable to a U.S. permanent establishment or fixed base maintained by the non-U.S. holder), in which case the gain would be subject to tax as described below under “— Income or Gains Effectively Connected with a U.S. Trade or Business”; or

• the non-U.S. holder is an individual who is present in the United States for 183 days or more in the year of disposition and certain other conditions apply, in which case, except as otherwise provided by an applicable income tax treaty, the gain, which may be offset by certain U.S.-source capital losses, would be subject to a flat 30% tax, even though the individual is not considered a resident of the United States.

Income or Gains Effectively Connected with a U.S. Trade or Business.

If any interest on the notes or gain from the sale, exchange, redemption or other taxable disposition of the notes is effectively connected with a U.S. trade or business conducted by a non-U.S. holder, such income or gain will be subject to U.S. federal income tax on a net-income basis at the regular graduated rates and generally in the same manner applicable to U.S. holders. If the non-U.S. holder is eligible for the benefits of a tax treaty between the United States and its country of residence, any “effectively connected” income or gain generally will be subject to U.S. federal income tax on a net-income basis only if it is also attributable to a permanent establishment or fixed base maintained by it in the United States. Payments of interest that are effectively connected with a U.S. trade or business conducted by the non-U.S. holder (and, if an applicable tax treaty requires, attributable to a U.S. permanent establishment or fixed base), and therefore included in the gross income of a non-U.S. holder, will not be subject to the 30% withholding tax discussed above under “—Non-U.S. Holders—Payments of Interest”, provided that the non-U.S. Holder claims exemption from withholding by timely filing a properly completed and executed IRS Form W-8ECI, or any appropriate substitute or successor form as the IRS designates, as applicable, prior to payment. If the non-U.S. holder is classified as a corporation for U.S. federal income tax purposes, that portion of its earnings and profits that is effectively connected with its U.S. trade or business generally also will be subject to an additional “branch profits tax.” The branch profits tax rate is currently 30%, although an applicable income tax treaty might provide for a lower rate.

Backup Withholding and Information Reporting

The Code and U.S. Treasury regulations generally require persons who make specified payments to report the payments to the IRS. Among the specified payments are interest, dividends, and proceeds paid by brokers to their customers. This reporting regime is reinforced by “backup

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withholding” rules, which generally require the payor to withhold from payments subject to information reporting if the recipient has failed to provide a taxpayer identification number to the payor, furnished an incorrect identification number, failed to comply with applicable certification requirements or been repeatedly notified by the IRS that it has failed to report interest or dividends on its U.S. federal income tax returns. The backup withholding rate is currently 24% for payments made before January 1, 2026.

Payments of interest to U.S. holders of notes and payments made to U.S. holders by a broker upon a sale of notes generally will be subject to information reporting and backup withholding, unless the U.S. holder (1) is an exempt recipient, or (2) in the case of backup withholding, provides the payor with a correct taxpayer identification number and complies with applicable certification requirements. If a sale is made through a foreign office of a foreign broker, however, the sale will generally not be subject to either information reporting or backup withholding. This exception may not apply if the foreign broker is owned or controlled by U.S. persons, or is engaged in a U.S. trade or business.

The applicable withholding agent must report annually to the IRS the interest paid to each non-U.S. holder and the amount of tax withheld, if any, with respect to such interest, including any tax withheld pursuant to the rules described under “— Non-U.S. Holders — Payments of Interest” above and “— FATCA” below. Copies of these reports may be made available to tax authorities in the country where the non-U.S. holder resides. Payments to non-U.S. holders of interest on the notes may be subject to backup withholding unless the non-U.S. holder certifies its non-U.S. status on a properly completed and executed IRS Form W-8BEN or W-8BEN-E or appropriate substitute form. Payments made to non-U.S. holders by a broker upon a sale of the notes will not be subject to information reporting (except to the extent such payments are subject to withholding under FATCA, discussed below) or backup withholding as long as the non-U.S. holder certifies its non-U.S. status or otherwise establishes an exemption.

Backup withholding is not an additional tax. Any amounts withheld from a payment to a U.S. holder or non-U.S. holder with respect to the notes under the backup withholding rules generally will be allowed as a refund or can be credited against any U.S. federal income tax liability of the holder, provided the required information is timely furnished to the IRS. Non-U.S. holders should consult their own tax advisors regarding the applicability of these rules to their particular circumstances.

FATCA

Sections 1471 through 1474 of the Code and the U.S. Treasury regulations and administrative guidance thereunder, known as FATCA, generally impose a 30% U.S. withholding tax on certain U.S.-source payments, including interest (including original issue discount), dividends and other fixed or determinable annual or periodical gain, profits, and income, and on the gross proceeds from a sale or other disposition of property of a type which can produce U.S.-source interest or dividends (“Withholdable Payments”), if paid to a foreign financial institution (whether as a beneficial owner or intermediary), unless such institution (i) enters into an agreement with the U.S. Department of the Treasury to collect and provide to the U.S. Department of the Treasury substantial information regarding its U.S. account holders, including certain account holders that are foreign entities with U.S. owners, (ii) satisfies the requirements of an intergovernmental agreement entered into by such institution’s country of residence and the United States, or (iii) qualifies for an exemption. These withholding requirements generally currently apply to payments of interest on the notes. Under proposed U.S. Treasury regulations, this withholding tax will not apply to the gross proceeds from the sale or other disposition of the notes. The preamble to these proposed U.S. Treasury regulations indicates that taxpayers may rely on them pending their finalization. FATCA also generally imposes a withholding tax of 30% on Withholdable Payments made to a non-financial foreign entity unless such

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entity provides the withholding agent with a certification that it does not have any substantial U.S. owners or certification identifying the direct and indirect substantial U.S. owners of the entity, or unless an exemption applies. An intergovernmental agreement between the United States and the non-U.S. entity’s jurisdiction may modify these requirements.

If FATCA withholding is imposed, a beneficial owner (other than certain foreign financial institutions) generally will be entitled to a refund of any amounts withheld by filing a U.S. federal income tax return and, in the case of a non-financial foreign entity, providing the IRS with certain information regarding its substantial U.S. owners (unless an exception applies). Prospective investors are urged to consult their tax advisors regarding the possible implications of FATCA on their ownership and disposition of the notes.

THE U.S. FEDERAL INCOME TAX DISCUSSION SET FORTH ABOVE AS TO BOTH U.S. AND NON-U.S. HOLDERS IS INCLUDED FOR GENERAL INFORMATION ONLY AND MAY NOT BE APPLICABLE DEPENDING ON AN INVESTOR’S SITUATION. INVESTORS ARE URGED TO CONSULT THEIR TAX ADVISORS CONCERNING THE APPLICATION OF THE U.S. FEDERAL INCOME TAX LAWS TO THEIR PARTICULAR SITUATION, AS WELL AS ANY TAX CONSEQUENCES OTHER THAN FROM U.S. FEDERAL INCOME TAX LAWS (SUCH AS U.S. FEDERAL ESTATE AND GIFT TAX LAWS) AND THE LAWS OF ANY NON-U.S., U.S. STATE, LOCAL OR OTHER TAXING JURISDICTION OR THE CONSEQUENCES ARISING UNDER ANY TAX TREATY.

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UNDERWRITING

Citigroup Global Markets Inc., Goldman Sachs & Co. LLC and J.P. Morgan Securities LLC are acting as bookrunning managers of the offering and Citigroup Global Markets Inc. is acting as representative of the underwriters named below. Subject to the terms and conditions stated in the underwriting agreement dated the date of this prospectus supplement, each underwriter named below has severally agreed to purchase, and we have agreed to sell to that underwriter, the principal amounts of notes set forth opposite the underwriter’s name.

Underwriter	Principal amount of notes
Citigroup Global Markets Inc.	$	159,375,000
Goldman Sachs & Co. LLC.		57,375,000
J.P. Morgan Securities LLC.		57,375,000
BofA Securities, Inc.		38,250,000
PNC Capital Markets LLC		38,250,000
MUFG Securities Americas Inc.		26,562,500
Wells Fargo Securities, LLC		26,562,500
HSBC Securities (USA) Inc.		21,250,000
Total	$	425,000,000

The underwriting agreement provides that the obligations of the underwriters to purchase the notes included in this offering are subject to approval of legal matters by counsel and to other conditions. The underwriters reserve the right to withdraw, cancel or modify offers to the public and to reject orders in whole or in part. The underwriters are obligated to purchase all the notes if they purchase any of the notes. If an underwriter defaults, the underwriting agreement provides that the purchase commitments of the nondefaulting underwriters may be increased or the underwriting agreement may be terminated.

The underwriters propose to offer some of the notes directly to the public at the public offering prices set forth on the cover page of this prospectus supplement and some of the notes to dealers at the public offering price less a concession. The underwriters may allow, and dealers may reallow, a concession on sales to other dealers. After the initial offering of the notes to the public, the representative may change the public offering prices and concessions.

The following table shows the underwriting discounts and commissions that we are to pay to the underwriters in connection with this offering (expressed as a percentage of the principal amount of the notes).

	Paid by ATI
Per note		1.125	%
Total	$	4,781,250

We estimate that our total expenses for this offering will be approximately $1.5 million.

We have agreed to indemnify the underwriters against certain liabilities, including liabilities under the Securities Act, or to contribute to payments the underwriters may be required to make because of any of those liabilities.

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The notes are a new issue of securities with no established trading market. The notes will not be listed on any securities exchange or on any automated dealer quotation system. The underwriters may make a market in the notes after completion of the offering, but will not be obligated to do so and may discontinue any market-making activities at any time without notice. No assurance can be given as to the liquidity of the trading market for the notes or that an active public market for the notes will develop. If an active public market for the notes does not develop, the market price and liquidity of the notes may be adversely affected. If the notes are traded, they may trade at a discount from their initial offering price, depending on prevailing interest rates, the market for similar securities, our operating performance and financial condition, general economic conditions and other factors.

In connection with the offering, the underwriters may purchase and sell notes in the open market. Purchases and sales in the open market may include short sales, purchases to cover short positions and stabilizing purchases.

• Short sales involve secondary market sales by the underwriters of a greater number of notes than they are required to purchase in the offering.

• Covering transactions involve purchases of notes in the open market after the distribution has been completed in order to cover short positions.

• Stabilizing transactions involve bids to purchase notes so long as the stabilizing bids do not exceed a specified maximum.

Purchases to cover short positions and stabilizing purchases, as well as other purchases by the underwriters for their own accounts, may have the effect of preventing or retarding a decline in the market price of the notes. They may also cause the price of the notes to be higher than the price that would otherwise exist in the open market in the absence of these transactions. The underwriters may conduct these transactions in the over-the-counter market or otherwise. If the underwriters commence any of these transactions, they may discontinue them at any time without notice.

Certain of the underwriters or their affiliates have performed commercial banking, investment banking and advisory services for us from time to time for which they have received customary fees and reimbursement of expenses. The underwriters may, from time to time, engage in transactions with and perform services for us in the ordinary course of their business for which they may receive customary fees and reimbursement of expenses. In addition, affiliates of some of the underwriters are lenders, and in some cases agents or managers for the lenders, under our credit facility. We have also agreed to pay Citigroup Global Markets Inc. $350,000 for certain structuring services in connection with this offering.

In addition, in the ordinary course of their business activities, the underwriters and their affiliates may make or hold a broad array of investments and actively trade debt and equity securities (or related derivative securities) and financial instruments (including bank loans) for their own account and for the accounts of their customers. Such investments and securities activities may involve securities and/or instruments of ours or our affiliates. Certain of those underwriters or their affiliates that have a lending relationships with us routinely hedge, and certain other of those underwriters or their affiliates may hedge, their credit exposure to us consistent with their customary risk management policies. Typically, these underwriters and their affiliates would hedge such exposure by entering into transactions which consist of either the purchase of credit default swaps or the creation of short positions in our securities, including potentially the notes offered hereby. Any such credit default swaps or short positions could adversely affect future trading prices of the notes offered hereby. The underwriters and their affiliates may also make investment recommendations and/or publish or express

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independent research views in respect of such securities or financial instruments and may hold, or recommend to clients that they acquire, long and/or short positions in such securities and instruments.

We expect that delivery of the notes will be made to investors on or about August 11, 2023, which will be the fourth business day following the date of the final prospectus supplement (such settlement being referred to as “T+4”). Under Rule 15c6-1 under the Exchange Act, trades in the secondary market are required to settle in two business days, unless the parties to any such trade expressly agree otherwise. Accordingly, purchasers who wish to trade notes prior to the delivery of the notes hereunder on a day prior to the second business day before the date of initial delivery of the notes will be required, by virtue of the fact that the notes initially settle in T+4, to specify an alternate settlement arrangement at the time of any such trade to prevent a failed settlement. Purchasers of the notes who wish to trade the notes prior to their date of delivery hereunder should consult their advisors.

Selling Restrictions

Notice to Prospective Investors in the European Economic Area

The notes are not intended to be offered, sold or otherwise made available to and should not be offered, sold or otherwise made available to any retail investor in the European Economic Area (“EEA”). For these purposes,

(a) a “retail investor” means a person who is one (or more) of the following:

a. a retail client as defined in point (11) of Article 4(1) of Directive 2014/65/EU (as amended, “MiFID II”); or

b. a customer within the meaning of Directive (EU) 2016/97 (as amended, the “Insurance Distribution Directive”), where that customer would not qualify as a professional client as defined in point (10) of Article 4(1) of MiFID II; or

c. not a qualified investor as defined in Regulation (EU) 2017/1129 (as amended, the “Prospectus Regulation”); and

(b) the expression an “offer” includes the communication in any form and by any means of sufficient information on the terms of the offer and the notes to be offered so as to enable an investor to decide to purchase or subscribe for the notes.

Consequently, no key information document required by Regulation (EU) No 1286/2014 (as amended, the “PRIIPs Regulation”) for offering or selling the notes or otherwise making them available to retail investors in the EEA has been prepared and therefore offering or selling the notes or otherwise making them available to any retail investor in the EEA may be unlawful under the PRIIPs Regulation. This prospectus supplement and the accompanying prospectus are not a prospectus for the purposes of the EU Prospectus Regulation.

Notice to Prospective Investors in the United Kingdom

The notes are not intended to be offered, sold or otherwise made available to and should not be offered, sold or otherwise made available to any retail investor in the United Kingdom (“UK”). For these purposes, a retail investor means a person who is one (or more) of: (i) a retail client, as defined in point (8) of Article 2 of Regulation (EU) No 2017/565 as it forms part of domestic law by virtue of the European Union (Withdrawal) Act 2018 (“EUWA”); (ii) a customer within the meaning of the provisions of the Financial Services and Markets Act 2000 (as amended, “FSMA”) and any rules or regulations made under the FSMA to implement Directive (EU) 2016/97, where that customer would not qualify as a professional client, as defined in point (8) of Article 2(1) of Regulation (EU) No 600/2014 as it forms part of domestic law by virtue of the EUWA; or (iii) not a qualified investor as

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defined in Article 2 of Regulation (EU) 2017/1129 as it forms part of domestic law by virtue of the EUWA (the “UK Prospectus Regulation”). For the purpose of this provision, the expression “an offer” includes the communication in any form and by any means of sufficient information on the terms of the offer and the notes to be offered so as to enable an investor to decide to purchase or subscribe for the notes”. Consequently, no key information document required by Regulation (EU) No 1286/2014 as it forms part of domestic law by virtue of the EUWA (the “UK PRIIPs Regulation”) for offering or selling the notes or otherwise making them available to retail investors in the UK has been prepared and therefore offering or selling the notes or otherwise making them available to any retail investor in the UK may be unlawful under the UK PRIIPs Regulation.

This prospectus supplement has been prepared on the basis that any offer of notes in the UK will be made pursuant to an exemption under the UK Prospectus Regulation from the requirement to publish a prospectus for offers of notes. This prospectus supplement is not a prospectus for the purposes of the UK Prospectus Regulation.

This prospectus supplement and the accompanying prospectus is only being distributed to, and is only directed at qualified investors within the meaning of Article 2(1)(e) of the UK Prospectus Regulation who are: (i) persons who are outside the UK, (ii) persons who have professional experience in matters relating to investments falling within Article 19(5) of the Financial Services and Markets Act 2000 (Financial Promotion) Order 2005 (as amended, the “Order”); (iii) high net worth entities falling within Article 49(2)(a) to (e) of the Order; and/or (iv) persons to whom an invitation or inducement to engage in investment activity (within the meaning of section 21 of the Financial Services and Markets Act 2000) may otherwise lawfully be communicated or caused to be communicated (all such persons together being referred to as “relevant persons”). Accordingly, such documents and/or materials are not being distributed to, and must not be passed on to, the general public in the UK. This prospectus supplement and the accompanying prospectus is directed only at relevant persons and must not be acted on or relied on in the UK by persons who are not relevant persons. In the UK, any investment or investment activity to which this prospectus supplement and the accompanying prospectus relates is available only to relevant persons and will be engaged in only with relevant persons.

Notice to Prospective Investors in Canada

The notes may be sold only to purchasers purchasing, or deemed to be purchasing, as principal that are accredited investors, as defined in National Instrument 45-106 Prospectus Exemptions or subsection 73.3(1) of the Securities Act (Ontario), and are permitted clients, as defined in National Instrument 31-103 Registration Requirements, Exemptions and Ongoing Registrant Obligations. Any resale of the notes must be made in accordance with an exemption from, or in a transaction not subject to, the prospectus requirements of applicable securities laws.

Securities legislation in certain provinces or territories of Canada may provide a purchaser with remedies for rescission or damages if this prospectus supplement and the accompanying prospectus (including any amendment thereto) contains a misrepresentation, provided that the remedies for rescission or damages are exercised by the purchaser within the time limit prescribed by the securities legislation of the purchaser’s province or territory. The purchaser should refer to any applicable provisions of the securities legislation of the purchaser’s province or territory for particulars of these rights or consult with a legal advisor.

Pursuant to section 3A.3 of National Instrument 33-105 Underwriting Conflicts (NI 33-105), the underwriters are not required to comply with the disclosure requirements of NI 33-105 regarding underwriter conflicts of interest in connection with this offering.

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LEGAL MATTERS

The validity of the notes offered hereby will be passed upon for us by K&L Gates LLP, Pittsburgh, Pennsylvania. The underwriters have been represented in connection with this offering by Cravath, Swaine  & Moore LLP, New York, New York.

EXPERTS

The consolidated financial statements of ATI Inc. and Subsidiaries appearing in ATI Inc.’s Annual Report (Form 10-K) for the year ended December 31, 2022, and the effectiveness of ATI Inc. and Subsidiaries’ internal control over financial reporting as of December 31, 2022, have been audited by Ernst & Young LLP, an independent registered public accounting firm, as set forth in their reports thereon, included therein, and incorporated herein by reference. Such consolidated financial statements have been incorporated herein by reference in reliance upon such reports given on the authority of such firm as experts in accounting and auditing.

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PROSPECTUS

Allegheny Technologies Incorporated

Debt Securities

Preferred Stock

Common Stock

Warrants

Purchase Contracts

Purchase Units

Depositary Shares

We may, from time to time, offer to sell, in one or more series, senior or subordinated debt securities, preferred stock, common stock, warrants, purchase contracts, purchase units or depositary shares, or any combination of these securities. The debt securities, preferred stock, warrants and purchase contracts may be convertible into or exercisable or exchangeable for our common or preferred stock or other securities or debt or equity securities of one or more other entities.

Our common stock is listed on the New York Stock Exchange and trades under the ticker symbol “ATI.” If we decide to seek a listing of any securities offered by this prospectus, we will disclose the exchange or market on which the securities will be listed or where we have made an application for listing in one or more supplements to this prospectus.

This prospectus describes some of the general terms that may apply to these securities. The specific terms of any securities to be offered, and the specific manner in which they may be offered, will be described in one or more supplements to this prospectus. This prospectus may not be used to sell securities unless it is accompanied by a prospectus supplement that contains a description of those securities.

We may offer and sell these securities to or through one or more underwriters, dealers or agents, or directly to other purchasers, on a continuous or delayed basis. If any offering involves underwriters, dealers or agents, arrangements with them will be described in a prospectus supplement relating to that offering.

We urge you to carefully read the information included or incorporated by reference in this prospectus and any prospectus supplement for a discussion of factors you should consider before deciding to invest in any securities offered by this prospectus, including the information under “Risk Factors” on page 1 of this prospectus.

Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of these securities or passed upon the adequacy or accuracy of this prospectus. Any representation to the contrary is a criminal offense.

The date of this Prospectus is March 31, 2021.

TABLE OF CONTENTS

ABOUT THIS PROSPECTUS	i
WHERE YOU CAN FIND MORE INFORMATION	ii
SUMMARY	1
RISK FACTORS	1
FORWARD-LOOKING STATEMENTS	1
USE OF PROCEEDS	2
DESCRIPTION OF DEBT SECURITIES	3
DESCRIPTION OF OTHER SECURITIES	22
DESCRIPTION OF CAPITAL STOCK	23
PLAN OF DISTRIBUTION	28
LEGAL MATTERS	30
EXPERTS	30

ABOUT THIS PROSPECTUS

This prospectus is part of a registration statement that we have filed with the Securities and Exchange Commission (the “SEC”), using an automatic shelf registration process. By using a shelf registration statement, we may sell, from time to time, in one or more offerings, any combination of the securities described in this prospectus. This prospectus does not contain all of the information in that registration statement. For further information about our business and the securities that may be offered under this prospectus, you should refer to the registration statement and its exhibits. The exhibits to the registration statement contain the full text of certain contracts and other important documents that we have summarized in this prospectus. Since the summaries in this prospectus may not contain all the information that you may find important in deciding whether to purchase the securities we may offer, you should review the full text of these contracts and documents. These summaries are qualified in all respects by reference to all of the provisions contained in the applicable contract or document. The registration statement and its exhibits can be obtained from the SEC as indicated under the heading “Where You Can Find More Information.”

This prospectus only provides you with a general description of the securities we may offer. Each time we sell securities, we will provide a prospectus supplement that contains specific information about the terms of those securities. The prospectus supplement may also add, update or change information contained in this prospectus. You should read this prospectus and any applicable prospectus supplement together with the additional information described below under the heading “Where You Can Find More Information.”

You should rely only on the information contained or incorporated by reference in this prospectus and any applicable prospectus supplement. We have not authorized anyone to provide you with different information. We are not making an offer to sell these securities in any jurisdiction where the offer or sale is not permitted. You should not assume that the information in this prospectus, any prospectus supplement or any document incorporated herein by reference is accurate as of any date other than the date of the applicable document. Our business, financial condition, results of operations and prospects may have changed since that date.

i

WHERE YOU CAN FIND MORE INFORMATION

Available Information

We file reports, proxy statements and other information with the SEC. The SEC maintains an internet site that contains reports, proxy and information statements and other information regarding issuers that file electronically with the SEC, including us. The SEC’s internet address is http://www.sec.gov. In addition, our common stock is listed on the New York Stock Exchange, and our reports and other information can be inspected at the offices of the New York Stock Exchange, 20 Broad Street, New York, New York 10005. Our Internet website is www.atimetals.com. Information contained on our website is not part of, and should not be construed as being incorporated by reference into, this prospectus.

Incorporation by Reference

The SEC allows us to “incorporate by reference” information that we file with it. This means that we can disclose important information to you by referring you to other documents. Any information we incorporate in this manner is considered part of this prospectus except to the extent updated and superseded by information contained in this prospectus. Some information that we file with the SEC after the date of this prospectus and until we sell all of the securities covered by this prospectus will automatically update and supersede the information contained in this prospectus.

We incorporate by reference the following documents that we have filed with the SEC and any filings that we make with the SEC in the future under Sections 13(a), 13(c), 14 or 15(d) of the Securities Exchange Act of 1934, as amended (the “Exchange Act”), until we sell all of the securities covered by this prospectus, including between the date of this prospectus and the date on which the offering of the securities under this prospectus is terminated, except as noted in the paragraph below:

Our SEC Filings (File No. 1-12001)	Period for or Date of Filing
Annual Report on Form 10-K	Year Ended December 31, 2020
Current Reports on Form 8-K	March 2, 2021
Registration Statement on Form 8-A	July 30, 1996

Pursuant to General Instruction B of Form 8-K, any information submitted under Item 2.02, Results of Operations and Financial Condition, or Item 7.01, Regulation FD Disclosure, of Form 8-K is not deemed to be “filed” for the purpose of Section 18 of the Exchange Act, and we are not subject to the liabilities of Section 18 with respect to information submitted under Item 2.02 or Item 7.01 of Form 8-K. We are not incorporating by reference any information submitted under Item 2.02 or Item 7.01 of Form 8-K into any filing under the Securities Act of 1933, as amended (the “Securities Act”), or the Exchange Act or into this prospectus.

Statements contained in this prospectus as to the contents of any contract, agreement or other document referred to in this prospectus do not purport to be complete, and where reference is made to the particular provisions of that contract, agreement or other document, those references are qualified in all respects by reference to all of the provisions contained in that contract or other document. For a more complete understanding and description of each such contract, agreement or other document, we urge you to read the documents filed as exhibits to the registration statement of which the accompanying prospectus is a part.

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Any statement contained in a document incorporated by reference, or deemed to be incorporated by reference, into this prospectus will be deemed to be modified or superseded for purposes of this prospectus to the extent that a statement contained herein, therein or in any other subsequently filed document which also is incorporated by reference in this prospectus modifies or supersedes that statement. Any such statement so modified or superseded will not be deemed, except as so modified or superseded, to constitute a part of this prospectus.

We will provide without charge, upon written or oral request, a copy of any or all of the documents that are incorporated by reference into this prospectus and a copy of any or all other contracts, agreements or documents which are referred to in this prospectus. Requests should be directed to: Allegheny Technologies Incorporated, 1000 Six PPG Place, Pittsburgh, PA 15222-5479, Attention: Corporate Secretary; telephone number: (412) 394-2800. You also may review a copy of the registration statement and its exhibits through the SEC’s internet site.

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SUMMARY

This summary highlights selected information contained elsewhere in this prospectus and the documents incorporated by reference in this prospectus. Because the following is only a summary, it does not contain all of the information that may be important to you. You should carefully read this prospectus, any accompanying prospectus supplement and the documents incorporated by reference in this prospectus and any accompanying prospectus supplement before deciding whether to invest in any of our securities. References to the “Company”, “we”, “our” and “us” and similar terms means Allegheny Technologies Incorporated and its subsidiaries, unless the context otherwise requires.

Allegheny Technologies Incorporated

We are a global manufacturer of technically advanced specialty materials and complex components. Our largest markets are aerospace & defense, led by products for jet engines. Additionally, we have a strong presence in the energy markets, including oil & gas, downstream processing, and specialty energy. We are a market leader in manufacturing differentiated products that require our materials science capabilities and unique process technologies, including our new product development competence.

Our principal executive offices are located at 1000 Six PPG Place, Pittsburgh, PA 15222, and our telephone number is (412) 394-2800. Our common stock is quoted on the New York Stock Exchange under the symbol “ATI”.

RISK FACTORS

Investing in our securities involves risks. Before deciding to purchase any of our securities, you should carefully consider the discussion of risks and uncertainties under the heading “Risk Factors” contained in our Annual Report on Form 10-K for the fiscal year ended December 31, 2020, which is incorporated by reference in this prospectus, and under similar headings in our subsequently filed quarterly reports on Form 10-Q and annual reports on Form 10-K, as well as the other risks and uncertainties described in any applicable prospectus supplement and in the other documents incorporated by reference in this prospectus. See the information under the heading “Where You Can Find More Information” for information on how to obtain copies of documents incorporated by reference in this prospectus. The risks and uncertainties we discuss in the documents incorporated by reference in this prospectus are those we currently believe may materially affect our company. Additional risks and uncertainties not presently known to us or that we currently believe are immaterial also may materially and adversely affect our business, financial condition and results of operations.

FORWARD-LOOKING STATEMENTS

You should carefully review the information contained in or incorporated by reference into this prospectus. In this prospectus, statements that are not reported financial results or other historical information are “forward-looking statements.” Forward-looking statements give current expectations or forecasts of future events and are not guarantees of future performance. They are based on our management’s expectations that involve a number of business risks and uncertainties, any of which could cause actual results to differ materially from those expressed in or implied by the forward-looking statements.

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You can identify these forward-looking statements by the fact that they do not relate strictly to historic or current facts. They use words such as “anticipates,” “believes,” “estimates,” “expects,” “would,” “should,” “will,” “will likely result,” “forecast,” “outlook,” “projects,” and similar expressions in connection with any discussion of future operating or financial performance.

We cannot guarantee that any forward-looking statements will be realized, although we believe that we have been prudent in our plans and assumptions. Achievement of future results is subject to risks, uncertainties and assumptions that may prove to be inaccurate. Among others, the factors discussed in the “Risk Factors” section of our Annual Report on Form 10-K for our fiscal year ended December 31, 2020 and any of our subsequently filed Quarterly Reports on Form 10-Q, as well as the other risks and uncertainties described in any applicable prospectus supplement and in the other documents incorporated by reference in this prospectus, could cause actual results to differ from those in forward-looking statements included in or incorporated by reference into this prospectus or that we otherwise make. Should known or unknown risks or uncertainties materialize, or should underlying assumptions prove to be inaccurate, actual results could vary materially from those anticipated, estimated or projected. You should bear this in mind as you consider any forward-looking statements.

We undertake no obligation to publicly update forward-looking statements, whether as a result of new information, future events or otherwise, except as may be required by law. You are advised, however, to consider any additional disclosures that we may make on related subjects in future filings with the SEC. You should understand that it is not possible to predict or identify all factors that could cause our actual results to differ. Consequently, you should not consider any list of factors to be a complete set of all potential risks or uncertainties.

USE OF PROCEEDS

We intend to use the net proceeds from the sale of the securities for general corporate purposes unless otherwise indicated in the applicable prospectus supplement relating to a specific issuance of securities. Our general corporate purposes include, but are not limited to, repayment, redemption or refinancing of debt, capital expenditures, investments in or loans to subsidiaries and joint ventures, funding of possible acquisitions, working capital, contributions to one or more of our pension plans, satisfaction of other obligations and repurchase of our outstanding equity securities. Pending any such use, the net proceeds from the sale of the securities may be invested in short-term, investment grade, interest-bearing instruments. We will include a more detailed description of the use of proceeds of any specific offering under this prospectus in the applicable prospectus supplement relating to that offering.

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DESCRIPTION OF DEBT SECURITIES

General

We may issue debt securities in one or more series. When used in this “Description of Debt Securities” section, unless we state otherwise or the context clearly indicates otherwise, references to the “Company,” “we,” “us,” and “our” refer to Allegheny Technologies Incorporated and not any of its subsidiaries. We may issue senior or subordinated debt securities. Neither the senior debt securities nor the subordinated debt securities will be secured by any of our property or assets. Thus, by owning a debt security, you are one of our unsecured creditors.

The senior debt securities will constitute part of our senior debt, will be issued under one or more senior debt indentures between us and a trustee, as described below, and will rank equally with all of our other unsecured and unsubordinated debt. The subordinated debt securities will constitute part of our subordinated debt, will be issued under one or more subordinated debt indentures between us and the same or a different trustee, as described below, and will be subordinate in right of payment to all of our “senior debt,” as defined in the indenture with respect to such subordinated debt securities. The prospectus supplement for any series of subordinated debt securities or the information incorporated in this prospectus by reference will indicate the approximate amount of senior debt outstanding as of the end of the then most recent fiscal quarter. Neither indenture will limit our ability to incur additional senior debt or other indebtedness.

When we refer to “debt securities” in this prospectus, we mean both the senior debt securities and the subordinated debt securities. When we refer to a “debt security” in this prospectus, we mean either a senior debt security or a subordinated debt security. When we refer to an “indenture” in this prospectus, we mean a senior debt indenture or a subordinated debt indenture, as the context requires, and references to the “indentures” means, collectively, the one or more senior debt indentures and subordinated debt indentures into which we may enter from time to time, in each case in the respective forms filed as exhibits to the registration statement of which this prospectus is a part. When we refer to a “trustee” in this prospectus, we mean a trustee named as such under the applicable indenture.

The debt indentures and their associated documents, including the debt security, will contain the full legal text of the matters described in this section and the applicable prospectus supplement. We have filed forms of the indentures with the SEC as exhibits to our registration statement of which this prospectus is a part. See “Where You Can Find More Information” in this prospectus for information on how to obtain copies of the indentures.

This section and the applicable prospectus supplement summarize material terms of the indentures and the applicable debt security. They do not, however, describe every aspect of the indentures and the applicable debt security. For example, in this section and the applicable prospectus supplement, we use terms that have been given special meaning in the indentures, but we do not describe the meaning of all the terms that may be important to you. The applicable prospectus supplement will have a more detailed description of the specific terms of a debt security.

Indentures

The senior debt securities and subordinated debt securities each will be governed by a document called an indenture. Each indenture is a contract between us and a trustee to be named therein. The

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indentures are substantially identical, except for certain provisions including those relating to subordination, which are included only in the indenture related to subordinated debt securities.

The trustee under each indenture has two main roles:

• First, the trustee can enforce your rights against us if we default. There are some limitations on the extent to which the trustee acts on your behalf, which we describe later under “—  Default, Remedies and Waiver of Default.”

• Second, the trustee performs administrative duties for us, such as sending you interest payments and notices.

When we refer to the “indenture” or the “trustee” with respect to any debt securities, we mean the indenture under which those debt securities are issued and the trustee under that indenture.

Series of Debt Securities

We may issue as many distinct debt securities or series of debt securities under either indenture as we wish. This section summarizes terms of the securities that apply generally to all debt securities and series of debt securities. The provisions of each indenture allow us not only to issue debt securities with terms different from those of debt securities previously issued under that indenture, but also to “reopen” a previously issued series of debt securities and issue additional debt securities of that series. We will describe most of the financial and other specific terms of a debt security, whether it is a series of the senior debt securities or the subordinated debt securities, in the applicable prospectus supplement. Those terms may vary from the terms described here.

As you read this section, please remember that the specific terms of a debt security as described in the applicable prospectus supplement will supplement and, if applicable, modify or replace the general terms described in this section. If there are any differences between the applicable prospectus supplement and this prospectus with respect to a debt security, the applicable prospectus supplement will control. Thus, the statements we make in this section may not apply to a particular debt security.

When we refer to a “series of debt securities,” we mean a series of debt securities issued under the applicable indenture. When we refer to “a debt security,” we mean a series of debt securities offered pursuant to this prospectus. When we refer to “the applicable prospectus supplement,” we mean the prospectus supplement describing the specific terms of a particular debt security. The terms used in the applicable prospectus supplement will have the meanings described in this prospectus, unless otherwise specified.

Amounts of Issuances

Neither indenture will limit the aggregate amount of debt securities that we may issue or the number of series or the aggregate amount of any particular series. We may issue debt securities and other securities at any time without your consent and without notifying you. The indentures and the debt securities will not limit our ability to incur other indebtedness or to issue other securities other than as specified in a debt security, as applicable. Also, unless otherwise specified below or in the applicable prospectus supplement, we are not subject to financial or similar restrictions by the terms of the debt securities.

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Principal Amount, Stated Maturity and Maturity

Unless otherwise stated, the principal amount of a debt security means the principal amount payable at its stated maturity, unless that amount is not determinable, in which case the principal amount of a debt security is its face amount. The term “stated maturity” with respect to any debt security means the day on which the principal amount of a debt security is scheduled to become due. The principal may become due sooner, by reason of redemption, acceleration after a default or otherwise in accordance with the terms of the debt security. The day on which the principal actually becomes due, whether at the stated maturity or earlier, is called the “maturity” of the principal. We also use the terms “stated maturity” and “maturity” to refer to the days when other payments become due. For example, we may refer to a regular interest payment date when an installment of interest is scheduled to become due as the “stated maturity” of that installment. When we refer to the “stated maturity” or the “maturity” of a debt security without specifying a particular payment, we mean the stated maturity or maturity, as the case may be, of the principal.

Specific Terms of Debt Securities

The applicable prospectus supplement will describe the specific terms of a debt security, which will include some or all of the following:

• the title of the series of the debt security and whether it is a senior debt security or a subordinated debt security;

• any limit on the total principal amount of the debt securities of the same series;

• the stated maturity;

• the currency or currencies for payment of principal and interest, if not U.S. dollars;

• the price at which we originally issue the debt security, expressed as a percentage of the principal amount, and the original issue date;

• whether the debt security is a fixed-rate debt security, a floating rate debt security or an indexed debt security;

• if the debt security is a fixed-rate debt security, the yearly rate at which the debt security will bear interest, if any, and the interest payment dates;

• if the debt security is a floating-rate debt security, the interest rate basis; any applicable index currency or index maturity, spread or spread multiplier or initial base rate, maximum rate or minimum rate; the interest reset, determination, calculation and payment dates; the day count convention used to calculate interest payments for any period; the business day convention; and the calculation agent;

• if the debt security is an indexed debt security, the principal amount, if any, we will pay at maturity, interest payment dates, the amount of interest, if any, we will pay on an interest payment date or the formula we will use to calculate these amounts, if any, and the terms on which the debt security will be exchangeable for or payable in cash, securities or other property;

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• if the debt security may be converted into or exercised or exchanged for common or preferred stock or other securities of the Company or debt or equity securities of one or more third parties, the terms on which conversion, exercise or exchange may occur, including whether conversion, exercise or exchange is mandatory, at the option of the holder or at our option, the period during which conversion, exercise or exchange may occur, the initial conversion, exercise or exchange price or rate and the circumstances or manner in which the amount of common or preferred stock or other securities issuable upon conversion, exercise or exchange may be adjusted;

• if the debt security is also an original issue discount debt security, the yield to maturity;

• if applicable, the circumstances under which the debt security may be redeemed at our option or repaid at the holder’s option before the stated maturity, including any redemption commencement date, repayment date(s), redemption price(s) and redemption period(s);

• the authorized denominations, if other than $2,000 and any integral multiple of $1,000 in excess thereof;

• the depositary for the debt security, if other than The Depository Trust Company (“DTC”), and any circumstances under which the holder may request securities in non-global form, if we choose not to issue the debt security in book-entry form only;

• if applicable, the circumstances under which we will pay additional amounts on any debt securities held by a person who is not a United States person for tax purposes and under which we can redeem the debt securities if we have to pay additional amounts;

• the names and duties of any co-trustees, depositaries, authenticating agents, paying agents, transfer agents or registrars for the debt security, as applicable; and

• any other terms of the debt security, which could be different from those described in this prospectus.

Governing Law

The indentures and the debt securities will be governed by New York law.

Form of Debt Securities

We will issue each debt security only in registered form, without coupons, unless we specify otherwise in the applicable prospectus supplement. In addition, we will issue each debt security in global (i.e., book-entry) form only, unless we specify otherwise in the applicable prospectus supplement. Debt securities in book-entry form will be represented by a global security registered in the name of a depositary, which will be the holder of all the debt securities represented by the global security. Those who own beneficial interests in a global debt security will do so through participants in the depositary’s securities clearance system, and the rights of these indirect owners will be governed solely by the applicable procedures of the depositary and its participants. References to “holders” in this section mean those who own debt securities registered in their own names, on the books that we or the registrar maintain for this purpose, and not those who own beneficial interests in debt securities registered in street name or in debt securities issued in book-entry form through one or more depositaries.

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Unless otherwise indicated in the applicable prospectus supplement, the following is a summary of the depositary arrangements applicable to debt securities issued in global form and for which DTC acts as depositary.

Each global debt security will be deposited with, or on behalf of, DTC, as depositary, or its nominee, and registered in the name of a nominee of DTC. Except under the limited circumstances described below, global debt securities are not exchangeable for definitive certificated debt securities.

Ownership of beneficial interests in a global debt security is limited to institutions that have accounts with DTC or its nominee, or persons that may hold interests through those participants. In addition, ownership of beneficial interests by participants in a global debt security will be evidenced only by, and the transfer of that ownership interest will be effected only through, records maintained by DTC or its nominee for a global debt security. Ownership of beneficial interests in a global debt security by persons that hold those interests through participants will be evidenced only by, and the transfer of that ownership interest within that participant will be effected only through, records maintained by that participant. DTC has no knowledge of the actual beneficial owners of the debt securities. Beneficial owners will not receive written confirmation from DTC of their purchase, but beneficial owners are expected to receive written confirmations providing details of the transaction, as well as periodic statements of their holdings, from the participants through which the beneficial owners entered the transaction. The laws of some jurisdictions require that certain purchasers of securities take physical delivery of securities they purchase in definitive form. These laws may impair your ability to transfer beneficial interests in a global debt security.

We will make payment of principal of, and interest on, debt securities represented by a global debt security registered in the name of or held by DTC or its nominee to DTC or its nominee, as the case may be, as the registered owner and holder of the global debt security representing those debt securities. DTC has advised us that upon receipt of any payment of principal of, or interest on, a global debt security, DTC immediately will credit accounts of participants on its book-entry registration and transfer system with payments in amounts proportionate to their respective interests in the principal amount of that global debt security, as shown in the records of DTC. Payments by participants to owners of beneficial interests in a global debt security held through those participants will be governed by standing instructions and customary practices, as is now the case with securities held for the accounts of customers in bearer form or registered in “street name,” and will be the sole responsibility of those participants, subject to any statutory or regulatory requirements that may be in effect from time to time.

Neither we, any trustee nor any of our respective agents will be responsible for any aspect of the records of DTC, any nominee or any participant relating to, or payments made on account of, beneficial interests in a permanent global debt security or for maintaining, supervising or reviewing any of the records of DTC, any nominee or any participant relating to such beneficial interests.

A global debt security is exchangeable for definitive certificated debt securities registered in the name of, and a transfer of a global debt security may be registered to, any person other than DTC or its nominee, only if:

• DTC notifies us that it is unwilling, unable or no longer qualified to continue as depositary for that global security or has ceased to be a registered clearing agency and we do not appoint another institution to act as depositary within 60 days; or

• we notify the trustee that we wish to terminate that global security.

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Any global debt security that is exchangeable pursuant to the preceding paragraph will be exchangeable in whole for definitive certificated debt securities in registered form, of like tenor and of an equal aggregate principal amount as the global debt security, in denominations specified in the applicable prospectus supplement, if other than $2,000 and integral multiples of $1,000 in excess thereof. The definitive debt securities will be registered by the registrar in the name or names instructed by DTC. We expect that these instructions may be based upon directions received by DTC from its participants with respect to ownership of beneficial interests in the global debt security.

Except as provided above or in the applicable prospectus supplement, owners of the beneficial interests in a global debt security will not be entitled to receive physical delivery of debt securities in definitive certificated form and will not be considered the holders of debt securities for any purpose under the indentures. Except as provided above, no global debt security will be exchangeable except for another global debt security of like denomination and tenor to be registered in the name of DTC or its nominee. Accordingly, each person owning a beneficial interest in a global debt security must rely on the procedures of DTC and, if that person is not a participant, on the procedures of the participant through which that person owns its interest, to exercise any rights of a holder under the global debt security or the indentures.

We understand that, under existing industry practices, in the event that we request any action of holders, or an owner of a beneficial interest in a global debt security desires to give or take any action that a holder is entitled to give or take under the debt securities or the indentures, DTC would authorize the participants holding the relevant beneficial interests to give or take that action. Additionally, those participants would authorize beneficial owners owning through those participants to give or take that action or would otherwise act upon the instructions of beneficial owners owning through them.

DTC has advised us that it is a limited-purpose trust company organized under the laws of the State of New York, a “banking organization” within the meaning of the New York Banking Law, a member of the Federal Reserve System, a “clearing corporation” within the meaning of the New York Uniform Commercial Code, and a “clearing agency” registered under the Exchange Act. DTC was created to hold securities of its participants and to facilitate the clearance and settlement of transactions among its participants in securities through electronic book-entry changes in accounts of the participants. By doing so, DTC eliminates the need for physical movement of securities certificates. DTC’s participants include securities brokers and dealers, banks, trust companies, clearing corporations, and certain other organizations. DTC is a wholly owned subsidiary of The Depository Trust & Clearing Corporation (DTCC); DTCC is the holding company for DTC, National Securities Clearing Corporation and Fixed Income Clearing Corporation, all of which are registered clearing agencies; and DTCC is owned by the users of its regulated subsidiaries. Access to DTC’s book-entry system is also available to others, such as banks, brokers, dealers, and trust companies that clear through or maintain a custodial relationship with a participant, either directly or indirectly. The rules applicable to DTC and its participants are on file with the SEC.

Investors may hold interests in the debt securities outside the U.S. through the Euroclear System (“Euroclear”) or Clearstream Banking (“Clearstream”) if they are participants in those systems, or indirectly through organizations which are participants in those systems. Euroclear and Clearstream will hold interests on behalf of their participants through customers’ securities accounts in Euroclear’s and Clearstream’s names on the books of their respective depositaries, which in turn will hold such interests in customers’ securities accounts in the depositaries’ names on the books of DTC. All securities in Euroclear or Clearstream are held on a fungible basis without attribution of specific certificates to specific securities clearance accounts.

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The following is based on information furnished by Euroclear or Clearstream, as the case may be.

Euroclear has advised us that:

• It was created in 1968 to hold securities for participants of Euroclear and to clear and settle transactions between Euroclear participants through simultaneous electronic book-entry delivery against payment, thereby eliminating the need for physical movement of certificates and any risk from lack of simultaneous transfers of securities and cash;

• Euroclear includes various other services, including securities lending and borrowing and interfaces with domestic markets in several countries;

• Euroclear is operated by Euroclear Bank SA/NV, as operator of the Euroclear System (the “Euroclear Operator”), under contract with Euroclear Clearance Systems S.C., a Belgian cooperative corporation (the “Cooperative”);

• The Euroclear Operator conducts all operations, and all Euroclear securities clearance accounts and Euroclear cash accounts are accounts with the Euroclear Operator, not the Cooperative. The Cooperative establishes policy for Euroclear on behalf of Euroclear participants. Euroclear participants include banks (including central banks), securities brokers and dealers and other professional financial intermediaries and may include underwriters of debt securities offered by this prospectus;

• Indirect access to Euroclear is also available to other firms that clear through or maintain a custodial relationship with a Euroclear participant, either directly or indirectly;

• Securities clearance accounts and cash accounts with Euroclear SA/NV are governed by the Terms and Conditions Governing Use of Euroclear, the related Operating Procedures of Euroclear, and applicable Belgian law (collectively, the “Terms and Conditions”);

• The Terms and Conditions govern transfers of securities and cash within Euroclear, withdrawals of securities and cash within Euroclear, withdrawals of securities and cash from Euroclear, and receipts of payments with respect to securities in Euroclear. All securities in Euroclear are held on a fungible basis without attribution of specific certificates to specific securities clearance accounts. Euroclear SA/NV acts under the Terms and Conditions only on behalf of Euroclear participants and has no record of or relationship with persons holding through Euroclear participants; and

• Distributions with respect to debt securities held beneficially through Euroclear will be credited to the cash accounts of Euroclear participants in accordance with the Terms and Conditions, to the extent received by the U.S. depositary for Euroclear.

Clearstream has advised us that:

• It is incorporated under the laws of Luxembourg as a professional depositary and holds securities for its participating organizations and facilitates the clearance and settlement of securities transactions between Clearstream participants through electronic book-entry changes in accounts of Clearstream participants, thereby eliminating the need for physical movement of certificates;

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• Clearstream provides to Clearstream participants, among other things, services for safekeeping, administration, clearance and settlement of internationally traded securities and securities lending and borrowing. Clearstream interfaces with domestic markets in several countries;

• As a professional depositary, Clearstream is subject to regulation by the Luxembourg Monetary Institute;

• Clearstream participants are recognized financial institutions around the world, including underwriters, securities brokers and dealers, banks, trust companies, clearing corporations and certain other organizations and may include underwriters of debt securities offered by this prospectus;

• Indirect access to Clearstream is also available to others, such as banks, brokers, dealers and trust companies, that clear through or maintain a custodial relationship with a Clearstream participant either directly or indirectly; and

• Distributions with respect to the debt securities held beneficially through Clearstream will be credited to cash accounts of Clearstream participants in accordance with its rules and procedures, to the extent received by the U.S. depositary for Clearstream.

We have provided the descriptions herein of the operations and procedures of DTC, Euroclear and Clearstream solely as a matter of convenience. These operations and procedures are solely within the control of DTC, Euroclear and Clearstream and are subject to change by them from time to time. We believe that the sources from which the information in this section and elsewhere in this prospectus concerning DTC, Euroclear, Euroclear SA/NV, Euroclear Clearance Systems S.C., Euroclear’s system, Clearstream and Clearstream’s system has been obtained are reliable, but neither we, any underwriters nor the trustee takes any responsibility for the accuracy of the information.

Initial settlement for the securities will be made in immediately available funds. Secondary market trading between DTC participants will occur in the ordinary way in accordance with DTC’s rules and will be settled in immediately available funds. Secondary market trading between Euroclear participants and/or Clearstream participants will occur in the ordinary way in accordance with the applicable rules and operating procedures of Euroclear and Clearstream, as applicable, and will be settled using the procedures applicable to conventional eurobonds in immediately available funds.

Cross-market transfers between persons holding directly or indirectly through DTC, on the one hand, and directly or indirectly through Euroclear participants or Clearstream participants, on the other, will be effected in DTC in accordance with DTC rules on behalf of the relevant European international clearing system by its U.S. depositary; however, such cross-market transactions will require delivery of instructions to the relevant European international clearing system by the counterparty in such system in accordance with its rules and procedures and within its established deadlines (European time). The relevant European international clearing system will, if the transaction meets its settlement requirements, deliver instructions to its U.S. depositary to take action to effect final settlement on its behalf by delivering or receiving securities in DTC, and making or receiving payment in accordance with normal procedures for same-day funds settlement applicable to DTC. Euroclear participants and Clearstream participants may not deliver instructions directly to their respective U.S. depositaries.

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Because of time-zone differences, credits of securities received in Euroclear or Clearstream as a result of a transaction with a DTC participant will be made during subsequent securities settlement processing and dated the business day following the DTC settlement date. Credits or any transactions in securities settled during this processing will be reported to the relevant Euroclear or Clearstream participants on that following business day. Cash received in Euroclear or Clearstream as a result of sales of debt securities by or through a Euroclear participant or a Clearstream participant to a DTC participant will be received with value on the DTC settlement date but will be available in the relevant Euroclear or Clearstream cash account only as of the business day following settlement in DTC.

Although DTC, Euroclear and Clearstream have agreed to the foregoing procedures to facilitate transfers of securities among participants of DTC, Euroclear and Clearstream, they are under no obligation to perform or continue to perform these procedures and these procedures may be discontinued at any time.

Redemption or Repayment

If there are any provisions regarding redemption or repayment applicable to a debt security, we will describe them in the applicable prospectus supplement. We or our affiliates may purchase debt securities from investors who are willing to sell from time to time, either in the open market at prevailing prices or in private transactions at negotiated prices. Debt securities that we or they purchase may, at our discretion, be held, resold or canceled.

Mergers and Similar Transactions

We are generally permitted under the indentures to merge or consolidate with another corporation or other entity. We also are permitted under the indentures to sell all or substantially all of our assets to another corporation or other entity. With regard to any series of debt securities and other than as set forth in the applicable prospectus supplement, however, we may not take any of these actions unless all the following conditions, among other things, are met:

• If the successor entity in the transaction is not the Company, the successor entity must be organized as a corporation, limited liability company, partnership or trust and must expressly assume by supplemental indenture our obligations under the debt securities of that series and the indenture with respect to that series. The successor entity may be organized under the laws of any jurisdiction, whether in the United States or elsewhere.

• Immediately after the transaction, no default under the debt securities of that series has occurred and is continuing. For this purpose, “default under the debt securities of that series” means an event of default with respect to that series or any event that would be an event of default with respect to that series if the requirements for giving us default notice and for our default having to continue for a specific period of time were disregarded. We describe these matters below under “— Default, Remedies and Waiver of Default.”

• If the conditions described above are satisfied with respect to the debt securities of any series, we will not need to obtain the approval of the holders of those debt securities in order to merge or consolidate or to sell all or substantially all our assets. Also, these conditions will apply only if we wish to merge or consolidate with another entity or sell all or substantially all of our assets to another entity. We will not need to satisfy these conditions if we enter into

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other types of transactions, including any transaction in which we acquire the stock or assets of another entity, any transaction that involves a change of control of the Company but in which we do not merge or consolidate and any transaction in which we sell less than substantially all our assets.

The successor entity will be substituted for the Company with respect to the debt securities of any series and under the indenture with the same effect as if it had been an original party to the indenture, and, except in the case of a lease, the Company will be relieved from any further obligations and covenants under the indenture.

Subordination Provisions

Holders of subordinated debt securities should recognize that contractual provisions in the subordinated debt indenture may prohibit us from making payments on those securities. Subordinated debt securities are subordinate and junior in right of payment, to the extent and in the manner stated in the subordinated debt indenture, to all of our senior debt, as defined in the subordinated debt indenture, including all debt securities we have issued and will issue under the senior debt indenture.

The subordinated debt indenture will define “senior debt” as:

• our indebtedness under or in respect of our asset based lending credit facility, whether for principal, interest (including interest accruing after the filing of a petition initiating any proceeding pursuant to any bankruptcy law, whether or not the claim for such interest is allowed as a claim in such proceeding), reimbursement obligations, fees, commissions, expenses, indemnities or other amounts; and

• any other indebtedness permitted under the terms of that indenture, unless the instrument under which such indebtedness is incurred expressly provides that it is on a parity with or subordinated in right of payment to the subordinated debt securities.

Notwithstanding the foregoing, “senior debt” will not include: (i) equity interests; (ii) any liability for taxes; (iii) any indebtedness to any of our subsidiaries or affiliates; (iv) any trade payables; or (v) any indebtedness incurred in violation of the subordinated debt indenture.

We may modify the subordination provisions, including the definition of senior debt, with respect to one or more series of subordinated debt securities. Such modifications will be set forth in the applicable prospectus supplement.

The subordinated debt indenture provides that, unless all principal of and any premium or interest on the senior debt has been paid in full, no payment or other distribution may be made in respect of any subordinated debt securities in the following circumstances:

• in the event of any insolvency or bankruptcy proceedings, or any receivership, liquidation, reorganization, assignment for creditors or other similar proceedings or events involving us or our assets;

• (i) in the event and during the continuation of any default in the payment of principal of, and any premium and interest on, any senior debt beyond any applicable grace period or (ii) in

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the event that any event of default with respect to any senior debt has occurred and is continuing, permitting the holders of that senior debt (or a trustee) to accelerate the maturity of that senior debt, whether or not the maturity is in fact accelerated (unless, in the case of (i) or (ii), the payment default or event of default has been cured or waived or ceased to exist and any related acceleration has been rescinded) or (iii) in the event that any judicial proceeding is pending with respect to a payment default or event of default described in (i) or (ii); or

• in the event that any subordinated debt securities have been declared due and payable before their stated maturity.

If the trustee under the subordinated debt indenture or any holders of the subordinated debt securities receive any payment or distribution that is prohibited under the subordination provisions, then the trustee or the holders will have to repay that money to the holders of the senior debt.

Even if the subordination provisions prevent us from making any payment when due on the subordinated debt securities of any series, we will be in default on our obligations under that series if we do not make the payment when due. This means that the trustee under the subordinated debt indenture and the holders of that series can take action against us, but they will not receive any money until the claims of the holders of senior debt have been fully satisfied.

The subordinated debt indenture allows the holders of senior debt to obtain a court order requiring us and any holder of subordinated debt securities to comply with the subordination provisions.

Defeasance, Covenant Defeasance and Satisfaction and Discharge

When we use the term defeasance, we mean discharge from some or all of our obligations under the applicable indenture. If we deposit with the trustee funds or government securities, or if so provided in the applicable prospectus supplement, obligations other than government securities, sufficient to make payments on any series of debt securities on the dates those payments are due and payable and other specified conditions are satisfied, then, at our option, either of the following will occur:

• we will be discharged from our obligations with respect to the debt securities of such series (“legal defeasance”); or

• we will be discharged from any covenants we make in the applicable indenture for the benefit of such series and the related events of default will no longer apply to us (“covenant defeasance”).

If we defease any series of debt securities, the holders of such securities will not be entitled to the benefits of the applicable indenture, except for our obligations to register the transfer or exchange of such securities, replace stolen, lost or mutilated securities or maintain paying agencies and hold moneys for payment in trust. In case of covenant defeasance, our obligation to pay principal of, and any premium and interest on, the applicable series of debt securities will also survive.

We will be required to deliver to the trustee an opinion of counsel that the deposit and related defeasance would not cause the holders of the applicable series of debt securities to recognize gain or

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loss for federal income tax purposes. If we elect legal defeasance, that opinion of counsel must be based upon a ruling from the United States Internal Revenue Service or a change in law to that effect.

In addition, we may satisfy and discharge all our obligations under the indenture with respect to debt securities of any series, other than our obligation to register the transfer of and exchange debt securities of that series, provided that we either:

• deliver all outstanding debt securities of that series to the trustee for cancellation; or

• all such debt securities not so delivered for cancellation have either become due and payable or will become due and payable at their stated maturity within one year or are to be called for redemption within one year, and in the case of this bullet point, we have irrevocably deposited with the trustee in trust an amount of cash sufficient to pay the entire indebtedness of such debt securities, including interest to the stated maturity or applicable redemption date.

No Personal Liability

No past, present or future director, officer, employee, incorporator, member, manager, partner (whether general or limited), or stockholder of the Company, as such, will have any liability for any obligations of us under the debt securities or the indentures or for any claim based on, in respect of, or by reason of, such obligations or their creation. Each holder of debt securities by accepting a debt security waives and releases all such liability. The waiver and release are part of the consideration for issuance of the debt securities. The waiver may not be effective to waive liabilities under the federal securities laws.

Default, Remedies and Waiver of Default

You will have special rights if an event of default with respect to a debt security occurs and is continuing, as described in this subsection.

Events of Default

Unless the applicable prospectus supplement says otherwise, when we refer to an event of default with respect to any series of debt securities, we mean any of the following:

• we do not pay the principal of and any premium on any debt security of that series on the due date;

• we do not pay interest on any debt security of that series within 30 days after the due date;

• we do not deposit a sinking fund payment with regard to any debt security of that series within 60 days after the due date, but only if the payment is required under provisions described in the applicable prospectus supplement;

• we remain in breach of our covenants regarding mergers or sales of substantially all of our assets or any other covenant we make in the indenture for the benefit of the relevant series, for 90 days after we receive a notice of default stating that we are in breach and requiring us to remedy the breach, which notice must be sent by the trustee or the holders of at least 25% in principal amount of the relevant series of debt securities;

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• we file for bankruptcy or other events of bankruptcy, insolvency or reorganization relating to the Company occur; or

• if the applicable prospectus supplement states that any additional event of default applies to the series, that event of default occurs.

We may change, eliminate, or add to the events of default with respect to any particular series or any particular debt security or debt securities within a series, as indicated in the applicable prospectus supplement.

Remedies if an Event of Default Occurs

If you are the holder of a subordinated debt security, all the remedies available upon the occurrence of an event of default under the subordinated debt indenture will be subject to the restrictions on the subordinated debt securities described above under “— Subordination Provisions.”

Except as otherwise specified in the applicable prospectus supplement, if an event of default has occurred with respect to any series of debt securities and has not been cured or waived, the trustee or the holders of not less than 25% in principal amount of all debt securities of that series then outstanding may declare the entire principal amount of the debt securities of that series to be due immediately. Except as otherwise specified in the applicable prospectus supplement, if the event of default occurs because of events in bankruptcy, insolvency or reorganization relating to the Company, the entire principal amount of the debt securities of that series will be automatically accelerated, without any action by the trustee or any holder.

Each of the situations described above is called an acceleration of the stated maturity of the affected series of debt securities. Except as otherwise specified in the applicable prospectus supplement, if the stated maturity of any series is accelerated and a judgment for payment has not yet been obtained, the holders of a majority in principal amount of the debt securities of that series may cancel the acceleration for the entire series.

If an event of default occurs, the trustee will have special duties. In that situation, the trustee will exercise the rights and powers vested in it under the relevant indenture, and to use the same degree of care and skill in its exercise, that a prudent person would exercise or use under the circumstances in the conduct of such person’s own affairs.

Except as described in the prior paragraph, the trustee is not required to take any action under the relevant indenture at the request of any holders unless the holders offer the trustee protection satisfactory to the trustee from cost, expenses and liability. This is called security or indemnity. If the trustee is provided with security or indemnity satisfactory to it, the holders of a majority in principal amount of all debt securities of the relevant series may direct the time, method and place of conducting any lawsuit or other formal legal action seeking any remedy available to the trustee with respect to that series. These majority holders may also direct the trustee in performing any other action under the relevant indenture with respect to the debt securities of that series.

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Before you bypass the trustee and bring your own lawsuit or other formal legal action or take other steps to enforce your rights or protect your interests relating to any debt security, all of the following must occur:

• the holder of the debt security must give the trustee written notice that an event of default has occurred with respect to the debt securities of your series, and the event of default must not have been cured or waived;

• the holders of not less than 25% in principal amount of all debt securities of your series must make a written request that the trustee take action because of the default, and they or other holders must offer to the trustee indemnity satisfactory to the trustee against the cost, expense and other liabilities of taking that action;

• the trustee must not have taken action for 60 days after the above steps have been taken; and

• during those 60 days, the holders of a majority in principal amount of the debt securities of your series must not have given the trustee directions that are inconsistent with the written request of the holders of not less than 25% in principal amount of the debt securities of your series.

You are entitled at any time, however, to bring a lawsuit for the payment of money due on your debt security on or after its stated maturity (or, if your debt security is redeemable, on or after its redemption date).

Book-entry and other indirect owners should consult their banks or brokers for information on how to give notice or direction to or make a request of the trustee and how to declare or cancel an acceleration of the maturity.

Waiver of Default

The holders of not less than a majority in principal amount of the debt securities of any series may waive a default for all debt securities of that series. If this happens, the default will be treated as if it has not occurred. No one can waive a payment default on any debt security, however, without the approval of the particular holder of that debt security.

Annual Information about Defaults to the Trustee

We will furnish each trustee every year a written statement of two of our officers certifying that to their knowledge we are in compliance with the applicable indenture and the debt securities issued under it, or else specifying any default under the applicable indenture.

Modifications and Waivers

There are four types of changes we can make to either indenture and the debt securities or series of debt securities issued under that indenture.

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Changes Requiring Each Holder’s Approval

First, there are changes that cannot be made without the approval of each holder of a debt security affected by the change under the applicable indenture, including, among others:

• changing the stated maturity for any principal or interest payment on such debt security;

• reducing the principal amount, the amount payable on acceleration of the maturity after a default, the interest rate or the redemption price for such debt security;

• permitting redemption of such debt security if not previously permitted;

• impairing any right such holder may have to require purchase of its debt security;

• if such debt security constitutes a convertible debt security, impairing any right that a holder may have to convert such debt security;

• changing the currency of any payment on such debt security;

• changing the place of payment on such debt security;

• impairing such holder’s right to sue for payment of any amount due on its debt security;

• reducing the percentage in principal amount of the debt securities of any one or more affected series, taken separately or together, as applicable, and whether comprising the same or different series or less than all of the debt securities of a series, the approval of whose holders is needed to change the indenture or those debt securities or waive our compliance with the applicable indenture or to waive defaults; and

• changing the provisions of the applicable indenture dealing with modification and waiver in any other respect, except to increase any required percentage referred to above or to add to the provisions that cannot be changed or waived without approval of the holder of each affected debt security.

Changes Not Requiring Approval

The second type of change does not require any approval by holders of the debt securities affected. These changes are limited to clarifications and changes that would not adversely affect any debt securities of any series in any material respect. Nor do we need any approval to make changes that affect only debt securities to be issued under the applicable indenture after the changes take effect. We may also make changes or obtain waivers that do not adversely affect a particular debt security, even if they affect other debt securities. In those cases, we do not need to obtain the approval of the holder of the unaffected debt security; we need only obtain any required approvals from the holders of the affected debt securities. We also may make changes to conform the text of the applicable indenture or any debt securities to any provision of the “Description of Debt Securities “in this prospectus or the comparable section in the applicable prospectus supplement, to the extent such provision was intended to be a verbatim recitation of a provision of such indenture or debt securities.

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Modification of Subordination Provisions

We may not amend the indenture related to subordinated debt securities to alter the subordination of any outstanding subordinated debt securities without the written consent of each holder of senior debt then outstanding who would be adversely affected (or the group or representative thereof authorized or required to consent thereto pursuant to the instrument creating or evidencing, or pursuant to which there is outstanding, such senior debt). In addition, we may not modify the subordination provisions of the indenture related to subordinated debt securities in a manner that would adversely affect the subordinated debt securities of any one or more series then outstanding in any material respect, without the consent of the holders of a majority in aggregate principal amount of all affected series then outstanding, voting together as one class (and also of any affected series that by its terms is entitled to vote separately as a series, as described below).

Changes Requiring Majority Approval

Any other change to a particular indenture and the debt securities issued under that indenture would require the following approval:

• if the change affects only particular debt securities within a series issued under the applicable indenture, it must be approved by the holders of a majority in principal amount of such particular debt securities; or

• if the change affects debt securities of more than one series issued under the applicable indenture, it must be approved by the holders of a majority in principal amount of all debt securities of all such series affected by the change, with all such affected debt securities voting together as one class for this purpose and such affected debt securities of any series potentially comprising fewer than all debt securities of such series,

in each case, except as may otherwise be provided pursuant to such indenture for all or any particular debt securities of any series. This means that modification of terms with respect to certain securities of a series could be effectuated without obtaining the consent of the holders of a majority in principal amount of other securities of such series that are not affected by such modification.

The same majority approval would be required for us to obtain a waiver of any of our covenants in either indenture. Our covenants include the promises we make about merging or selling substantially all of our assets, which we describe above under “— Mergers and Similar Transactions.” If the holders approve a waiver of a covenant, we will not have to comply with it. The holders, however, cannot approve a waiver of any provision in a particular debt security, or in the applicable indenture as it affects that debt security, that we cannot change without the approval of the holder of that debt security as described above in “— Changes Requiring Each Holder’s Approval,” unless that holder approves the waiver.

We may issue particular debt securities or a particular series of debt securities, as applicable, that are entitled, by their terms, to separately approve matters (for example, modification or waiver of provisions in the applicable indenture) that would also, or otherwise, require approval of holders of a majority in principal amount of all affected debt securities of all affected series issued under such indenture voting together as a single class. Any such affected debt securities or series of debt securities would be entitled to approve such matters (i) pursuant to such special rights by consent of holders of a

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majority in principal amount of such affected debt securities or series of debt securities voting separately as a class and (ii) in addition, as described above, except as may otherwise be provided pursuant to the applicable indenture for such debt securities or series of debt securities, by consent of holders of a majority in principal amount of such affected debt securities or series of debt securities and all other affected debt securities of all series issued under such indenture voting together as one class for this purpose. We may issue series or debt securities of a series having these or other special voting rights without obtaining the consent of or giving notice to holders of outstanding debt securities or series.

Book-entry and other indirect owners should consult their banks or brokers for information on how approval may be granted or denied if we seek to change an indenture or any debt securities or request a waiver.

Special Rules for Action by Holders

Only holders of outstanding debt securities of the applicable series will be eligible to take any action under the applicable indenture, such as giving a notice of default, declaring an acceleration, approving any change or waiver or giving the trustee an instruction with respect to debt securities of that series. Also, we will count only outstanding debt securities in determining whether the various percentage requirements for taking action have been met. Any debt securities owned by us or any of our affiliates or surrendered for cancellation or for payment or redemption, for which money has been set aside in trust, are not deemed to be outstanding. Any required approval or waiver must be given by written consent.

In some situations, we may follow special rules in calculating the principal amount of debt securities that are to be treated as outstanding for the purposes described above. This may happen, for example, if the principal amount is payable in a non-U.S. dollar currency, increases over time or is not to be fixed until maturity.

We will generally be entitled to set any day as a record date for the purpose of determining the holders that are entitled to take action under either indenture. In certain limited circumstances, only the trustee will be entitled to set a record date for action by holders. If we or the trustee sets a record date for an approval or other action to be taken by holders, that vote or action may be taken only by persons or entities who are holders on the record date and must be taken during the period that we specify for this purpose, or that the trustee specifies if it sets the record date. We or the trustee, as applicable, may shorten or lengthen this period from time to time. This period, however, may not extend beyond the 180th day after the record date for the action. In addition, record dates for any global debt security may be set in accordance with procedures established by the depositary from time to time. Accordingly, record dates for global debt securities may differ from those for other debt securities.

Form, Exchange and Transfer

If any debt securities cease to be issued in registered global form, they will be issued:

• only in fully registered form;

• without interest coupons; and

• unless we indicate otherwise in the applicable prospectus supplement, in denominations of $2,000 and integral multiples of $1,000 in excess thereof.

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Holders may exchange their debt securities for debt securities of smaller denominations or combined into fewer debt securities of larger denominations, as long as the total principal amount is not changed. You may not exchange your debt securities for securities of a different series or having different terms, unless the applicable prospectus supplement and the supplemental indenture with respect to your debt securities provide for such exchange.

Holders may exchange or transfer their debt securities at the office of the trustee. They may also replace lost, stolen, destroyed or mutilated debt securities at that office. We have appointed the trustee to act as our agent for registering debt securities in the names of holders and transferring and replacing debt securities. We may appoint another entity to perform these functions or perform them ourselves.

Holders will not be required to pay a service charge to transfer or exchange their debt securities, but they may be required to pay for any tax or other governmental charge associated with the exchange or transfer. The transfer or exchange, and any replacement, will be made only if our transfer agent is satisfied with the holder’s proof of legal ownership. The transfer agent may require an indemnity before replacing any debt securities.

If we have designated additional transfer agents for a debt security, they will be named in the applicable prospectus supplement. We may appoint additional transfer agents or cancel the appointment of any particular transfer agent. We may also approve a change in the office through which any transfer agent acts.

If the debt securities of any series are redeemable and we redeem less than all those debt securities, we may block the transfer or exchange of those debt securities during the period beginning 15 days before the day we send the notice of redemption and ending on the day of that sending, in order to freeze the list of holders to prepare the sending of the notice. We may also refuse to register transfers of or exchange any debt security selected for redemption, except that we will continue to permit transfers and exchanges of the unredeemed portion of any debt security being partially redeemed.

If a debt security is issued as a global debt security, only DTC or other depositary will be entitled to transfer and exchange the debt security as described in this subsection because the depositary will be the sole holder of the debt security.

The rules for exchange described above apply to exchange of debt securities for other debt securities of the same series and kind. If a debt security is convertible, exercisable or exchangeable into or for a different kind of security, such as one that we have not yet issued, or for other property, the rules governing that type of conversion, exercise or exchange will be described in the applicable prospectus supplement.

Payments

We will pay interest, principal and other amounts payable with respect to the debt securities of any series to the holders of record of those debt securities as of the record dates and otherwise in the manner specified below or in the prospectus supplement for that series.

We will make payments on a global debt security in accordance with the applicable procedures of the depositary as in effect from time to time. Under those procedures, we will pay directly to the

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depositary, or its nominee, and not to any indirect owners who own beneficial interests in the global debt security. An indirect owner’s right to receive those payments will be governed by the rules and practices of the depositary and its participants.

We will make payments on a debt security in non-global, registered form as follows. We will pay interest that is due on an interest payment date by check mailed on the interest payment date to the holder at his or her address shown on the trustee’s records as of the close of business on the regular record date. We will make all other payments by check at the paying agent described below, against surrender of the debt security. All payments by check will be made in next-day funds — i.e., funds that become available on the day after the check is cashed.

Alternatively, if a non-global debt security has a face amount of at least $1,000,000 and the holder asks us to do so, we will pay any amount that becomes due on the debt security by wire transfer of immediately available funds to an account at a bank within the United States, on the due date. To request wire payment, the holder must give the paying agent appropriate wire transfer instructions at least five business days before the requested wire payment is due. In the case of any interest payment due on an interest payment date, the instructions must be given by the person or entity who is the holder on the relevant regular record date. In the case of any other payment, payment will be made only after the debt security is surrendered to the paying agent. Any wire instructions, once properly given, will remain in effect unless and until new instructions are given in the manner described above.

Book-entry and other indirect owners should consult their banks or brokers for information on how they will receive payments on their debt securities.

Regardless of who acts as paying agent, subject to applicable escheatment law, all money paid by us to a paying agent that remains unclaimed at the end of two years after the amount is due to a holder will be repaid to us. After that two-year period, the holder may look only to us for payment and not to the trustee, any other paying agent or anyone else.

Paying Agents

We may appoint one or more financial institutions to act as our paying agents, at whose designated offices debt securities in non-global entry form may be surrendered for payment at their maturity. We call each of those offices a paying agent. We may add, replace or terminate paying agents from time to time. We may also choose to act as our own paying agent. We will specify in the prospectus supplement for a debt security the initial location of each paying agent for that debt security. We must notify the trustee of changes in the paying agents.

Notices

Notices to be given to holders of a global debt security will be given only to the depositary, in accordance with its applicable procedures as in effect from time to time. Notices to be given to holders of debt securities not in global form will be sent by mail to the respective addresses of the holders as they appear on the books of the registrar and will be deemed given when mailed. Neither the failure to give any notice to a particular holder, nor any defect in a notice given to a particular holder, will affect the sufficiency of any notice given to another holder.

Book-entry and other indirect owners should consult their banks or brokers for information on how they will receive notices.

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Our Relationship with the Trustee

The prospectus supplement for a debt security will describe any material relationships we may have with the trustee with respect to that debt security.

The same financial institution may initially serve as the trustee for our senior debt securities and subordinated debt securities. Consequently, if an actual or potential event of default occurs with respect to any of these securities, the trustee may be considered to have a conflicting interest for purposes of the Trust Indenture Act of 1939. In that case, the trustee may be required to resign under one or more of the indentures, and we would be required to appoint a successor trustee. For this purpose, a “potential” event of default means an event that would be an event of default if the requirements for giving us default notice or for the default having to exist for a specific period of time were disregarded.

DESCRIPTION OF OTHER SECURITIES

We will set forth in the applicable prospectus supplement a description of any warrants, purchase contracts, purchase units or depositary shares that may be offered pursuant to this prospectus.

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DESCRIPTION OF CAPITAL STOCK

Common Stock

We may issue, either separately or together with other securities, including as a part of purchase units, shares of our common stock. Shares of common stock issued as part of purchase units may be attached to or separate from any other securities part of those purchase units. Under our Restated Certificate of Incorporation, we are authorized to issue up to 500,000,000 shares of our common stock. As of March 29, 2021, we had 127,203,072 shares of common stock issued and outstanding and had reserved approximately 7,934,803 million additional shares of common stock for issuance under our stock compensation plans.

A prospectus supplement relating to an offering of common stock or other securities convertible or exchangeable for, or exercisable into, common stock, or the settlement of which may result in the issuance of common stock, will describe the relevant terms of the offering, including the number of shares offered, any initial offering price and market price and dividend information, as well as, if applicable, information on other related securities.

The following summary is not complete and is not intended to give full effect to provisions of statutory or common law. You should refer to the applicable provisions of the following:

• The Delaware General Corporation Law, as it may be amended from time to time;

• Our Restated Certificate of Incorporation, as it may be amended or further restated from time to time; and

• Our Amended and Restated Bylaws, as they may be further amended or restated from time to time.

Dividends. The holders of our common stock are entitled to receive dividends when, as and if declared by our board of directors, out of funds legally available for their payment subject to the rights of holders of our preferred stock.

Voting Rights. The holders of our common stock are entitled to one vote per share on all matters submitted to a vote of stockholders.

Rights upon Liquidation. In the event of our voluntary or involuntary liquidation, dissolution or winding up, the holders of common stock will be entitled to share equally in any of our assets available for distribution after the payment in full of all debts and distributions and after the holders of all series of our outstanding preferred stock have received their liquidation preferences in full.

Miscellaneous. The outstanding shares of common stock are fully paid and nonassessable. The holders of common stock are not entitled to preemptive or redemption rights. Shares of common stock are not convertible into shares of any other class of capital stock. Computershare Shareowner Services LLC is the transfer agent and registrar for the common stock.

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Preferred Stock

We may elect to issue shares of our preferred stock from time to time, as described in the applicable prospectus supplement. We may issue shares of preferred stock separately or as a part of purchase units, and any such shares issued as part of purchase units may be attached to or separate from any other securities part of those purchase units. Shares of our preferred stock may have dividend, redemption, voting and liquidation rights taking priority over our common stock, and shares of our preferred stock may be convertible into our common stock.

Our Board of Directors is authorized, subject to any limitations prescribed by law, to provide for the issuance of shares of preferred stock in one or more series. In addition, our Board of Directors is authorized to establish from time to time the number of shares to be included in each series of preferred stock and to fix the designation, powers (including but not limited to voting powers, if any), preferences and rights of the shares of each series of preferred stock and any qualifications, limitations or restrictions of each series of preferred stock. The number of authorized shares of preferred stock may be increased or decreased (but not below the number of shares thereof then outstanding) by the affirmative vote of the holders of a majority of the outstanding common stock, without a vote of the holders of the preferred stock, or of any series of preferred stock, unless a vote of any such holders is required pursuant to the terms of any preferred stock.

Our Restated Certificate of Incorporation authorizes our Board of Directors without further stockholder action, to provide for the issuance of up to 50,000,000 shares of preferred stock, in one or more series. As of the date of this prospectus, no shares of preferred stock have been issued, and 50,000,000 shares of preferred stock are available for issuance. We have 6,000,000 shares of preferred stock designated as Series A Junior Participating Preferred Stock in connection with our prior rights agreement, leaving 44,000,000 shares of preferred stock remaining available for designation as of the date of this prospectus.

The particular terms of any series of preferred stock being offered by us under this prospectus will be described in the prospectus supplement relating to that series of preferred stock. Those terms may include:

• The title and liquidation preference per share of the preferred stock;

• The number of shares offered;

• The purchase price of the preferred stock;

• The dividend rate (or method of calculation), the dates on which dividends will be paid and the date from which dividends will begin to accumulate;

• Any redemption or sinking fund provisions of the preferred stock;

• Any conversion provisions of the preferred stock;

• The voting rights, if any, of the preferred stock; and

• Any additional dividend, liquidation, redemption, sinking fund and other rights, preferences, privileges, limitations and restrictions of the preferred stock.

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If the terms of any series of preferred stock being offered differ from the terms set forth in this prospectus, the definitive terms will be disclosed in the applicable prospectus supplement. The summary in this prospectus is not complete. You should refer to the applicable Certificate of Amendment to our Restated Certificate of Incorporation or certificate of designations, as the case may be, establishing a particular series of preferred stock, in either case which will be filed with the Secretary of State of the State of Delaware and the SEC in connection with an offering of preferred stock.

The preferred stock will, when issued, be fully paid and nonassessable.

Dividend Rights. The preferred stock will be preferred over our common stock as to payment of dividends. Before any dividends or distributions (other than dividends or distributions payable in common stock) on our common stock will be declared and set apart for payment or paid, the holders of shares of each series of preferred stock will be entitled to receive dividends when, as and if declared by our board of directors. We will pay those dividends either in cash, shares of common stock or preferred stock or otherwise, at the rate and on the date or dates set forth in the applicable prospectus supplement. With respect to each series of preferred stock, the dividends on each share of the series will be cumulative from the date of issue of the share unless another date is set forth in the applicable prospectus supplement relating to the series. Accruals of dividends will not bear interest.

Rights upon Liquidation. The preferred stock will be preferred over our common stock as to assets so that the holders of each series of preferred stock will be entitled to be paid, upon our voluntary or involuntary liquidation, dissolution or winding up and before any distribution is made to the holders of common stock, the amount set forth in the applicable prospectus supplement. However, in this case the holders of preferred stock will not be entitled to any other or further payment. If upon any liquidation, dissolution or winding up our net assets are insufficient to permit the payment in full of the respective amounts to which the holders of all outstanding preferred stock are entitled, our entire remaining net assets will be distributed among the holders of each series of preferred stock in amounts proportional to the full amounts to which the holders of each series are entitled.

Redemption. All shares of any series of preferred stock will be redeemable to the extent set forth in the prospectus supplement relating to the series. All shares of any series of preferred stock will be convertible into shares of our common stock or into shares of any other series of our preferred stock to the extent set forth in the applicable prospectus supplement.

Voting Rights. Except as indicated in the applicable prospectus supplement, the holders of preferred stock will be entitled to one vote for each share of preferred stock held by them on all matters properly presented to stockholders. The holders of common stock and the holders of all series of preferred stock will vote together as one class.

Additional Series of Preferred Stock. In the event of a proposed merger or tender offer, proxy contest or other attempt to gain control of us and not approved by our board of directors, it would be possible for the board to authorize the issuance of one or more series of preferred stock with voting rights or other rights and preferences which would impede the success of the proposed merger, tender offer, proxy contest or other attempt to gain control of us. This authority may be limited by applicable law, our Restated Certificate of Incorporation, as it may amended or further restated from time to time, and the applicable rules of the stock exchanges upon which the common stock is listed. The consent of our stockholders would not be required for any such issuance of preferred stock.

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Special Charter Provisions. Our Restated Certificate of Incorporation provides that:

• Our Board of Directors is classified into three classes;

• In addition to the requirements of law and the other provisions of our Restated Certificate of Incorporation, the affirmative vote of at least two-thirds of the outstanding shares of our common stock is required for the adoption or authorization of any of the following events unless the event has been approved at a meeting of our Board of Directors by the vote of more than two-thirds of the incumbent members of our Board of Directors:

• Any merger or consolidation of us with or into any other corporation;

• Any sale, lease, exchange, transfer or other disposition, but excluding a mortgage or any other security device, of all or substantially all of our assets;

• Any merger or consolidation of a Significant Shareholder (as defined in our Restated Certificate of Incorporation) with or into us or a direct or indirect subsidiary of ours;

• Any sale, lease, exchange, transfer or other disposition to us or to a direct or indirect subsidiary of ours of any of our common stock held by a Significant Shareholder or any other assets of a Significant Shareholder which, if included with all other dispositions consummated during the same fiscal year of ours by the same Significant Shareholder, would result in dispositions of assets having an aggregate fair value in excess of five percent of our total consolidated assets as shown on our certified balance sheet as of the end of the fiscal year preceding the proposed disposition;

• Any reclassification of our common stock, or any re-capitalization involving our common stock, consummated within five years after a Significant Shareholder becomes a Significant Shareholder, whereby the number of outstanding shares of common stock is reduced or any of those shares are converted into or exchanged for cash or other securities;

• Any dissolution; and

• Any agreement, contract or other arrangement providing for any of these transactions but notwithstanding anything not including any merger pursuant to the Delaware General Corporation Law, as amended from time to time, which does not require a vote of our stockholders for approval;

• Our stockholders may not alter, amend, supplement or repeal, or adopt any provision inconsistent with the purpose or intent of, certain provisions contained in our Restated Certificate of Incorporation other than by the affirmative vote of 75% of the combined voting power of all of our outstanding voting securities entitled to vote generally in an election of directors, voting together as a single class;

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• Our stockholders may not adopt, amend or repeal our Amended and Restated Bylaws other than by the affirmative vote of 75% of the combined voting power of all of our outstanding voting securities entitled to vote generally in an election of directors, voting together as a single class;

• Any action required or permitted to be taken by our stockholders must be effected at a duly called annual or special meeting of stockholders and may not be effected by the written consent of the stockholders; and

• Special meetings of the stockholders may be called at any time by a majority of our directors and may not be called by any other person or persons or in any other manner.

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PLAN OF DISTRIBUTION

We may sell the securities in one or more of the following ways:

• To underwriters, whether or not part of a syndicate, for public offering and sale by them;

• Directly to purchasers in negotiated sales or in competitively bid transactions;

• Through agents;

• Through dealers; or

• Through a combination of any of the above methods of sale.

Offers to purchase securities may be solicited directly by us or by agents designated by us from time to time. Any agent, who may be deemed to be an underwriter, as that term is defined in the Securities Act, involved in the offer and sale of the securities will be named, and any commissions payable by us to that agent will be provided, in an applicable prospectus supplement. We and our agents may sell the securities at:

• A fixed price or prices, which may be changed;

• Market prices prevailing at the time of sale;

• Prices related to such prevailing market prices; or

• Negotiated prices.

Underwriters, dealers and agents participating in the distribution of the securities may be deemed to be underwriters, and any discounts and commissions received by them and any profit realized by them on resale of the securities may be deemed to be underwriting discounts and commissions under the Securities Act. Underwriters, dealers and agents may be entitled, under agreements with us, to indemnification against and contribution toward certain civil liabilities, including liabilities under the Securities Act, and to reimbursement by us for certain expenses. Unless otherwise described in an applicable prospectus supplement, the obligations of the underwriters to purchase offered securities will be subject to conditions, and the underwriters must purchase all of the offered securities if any are purchased.

If an underwriter or underwriters are used in the offer or sale of securities, we will execute an underwriting agreement with the underwriters at the time of sale of the securities to the underwriters, and the names of the underwriters and the principal terms of our agreements with the underwriters will be provided in an applicable prospectus supplement.

The securities subject to the underwriting agreement may be acquired by the underwriters for their own account and may be resold by them from time to time in one or more transactions, including negotiated transactions, at a fixed offering price or at varying prices determined at the time of sale. Underwriters may be deemed to have received compensation from us in the form of underwriting discounts or commissions and may also receive commissions from the purchasers of these securities for whom they may act as agent. Underwriters may sell these securities to or through dealers. These

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dealers may receive compensation in the form of discounts, concessions or commissions from the underwriters and commissions from the purchasers for whom they may act as agent. Any initial offering price and any discounts or concessions allowed or re-allowed or paid to dealers may be changed from time to time.

In connection with underwritten offerings of the securities, the underwriters may engage in over-allotment, stabilizing transactions, covering transactions and penalty bids in accordance with Regulation M under the Exchange Act, as follows:

• Over-allotment transactions that involve sales in excess of the offering size, which create a short position for the underwriters;

• Stabilizing transactions that permit bids to purchase the underlying security so long as the stabilizing bids do not exceed a specified maximum;

• Covering transactions that involve purchases of the securities in the open market after the distribution has been completed in order to cover short positions; and

• Penalty bids that permit the underwriters to reclaim a selling concession from a broker/dealer when the securities originally sold by that broker-dealer are repurchased in a covering transaction to cover short positions.

These stabilizing transactions, covering transactions and penalty bids may cause the price of the securities to be higher than it otherwise would be in the absence of these transactions. If these transactions occur, they may be discontinued at any time.

If indicated in an applicable prospectus supplement, we will authorize dealers acting as agents for us to solicit offers by certain institutions to purchase securities from us at the public offering price set forth in the prospectus supplement under delayed delivery contracts providing for payment and delivery on the date or dates stated in the prospectus supplement. The identity of any such agents, the terms of such delayed delivery contracts and the commissions payable by us to these agents will be set forth in an applicable prospectus supplement.

If indicated in an applicable prospectus supplement, we may sell shares of our common stock under a newly established direct stock purchase and dividend reinvestment plan. The terms of any such plan will be set forth in the applicable prospectus supplement.

Each underwriter, dealer and agent participating in the distribution of any of the securities that are issuable in bearer form will agree that it will not offer, sell or deliver, directly or indirectly, securities in bearer form in the United States or to U.S. persons, other than qualifying financial institutions, during the restricted period, as defined in U.S. Treasury Regulations Section 1.163-5(c)(2)(i)(D)(7).

Except for shares of our common stock or as otherwise described in an applicable prospectus supplement, all of the securities will be a new issue of securities with no established trading market. Any underwriters to whom or agents through whom the securities are sold by us for public offering and sale may make a market in the securities, but such underwriters or agents will not be obligated to do so and may discontinue any market making at any time without notice. No assurance can be given as to the liquidity of the trading market for any such securities.

Certain of the underwriters, dealers or agents and their associates may be customers of, engage in transactions with and perform services for us and our subsidiaries in the ordinary course of business.

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LEGAL MATTERS

Unless otherwise indicated in the applicable prospectus supplement, the validity of the securities offered by us will be passed upon for us by Elliot S. Davis, Senior Vice President, General Counsel, Chief Compliance Officer and Corporate Secretary of Allegheny Technologies Incorporated, or by K&L Gates LLP, Pittsburgh, Pennsylvania. Mr. Davis is paid a salary by Allegheny Technologies Incorporated, is a participant in various employee benefit plans offered to its employees and beneficially owns, or has rights to acquire, an aggregate of less than one percent of the shares of our outstanding common stock.

EXPERTS

The consolidated financial statements of Allegheny Technologies Incorporated appearing in Allegheny Technologies Incorporated’s Annual Report (Form 10-K) for the year ended December 31, 2020, and the effectiveness of Allegheny Technologies Incorporated’s internal control over financial reporting as of December 31, 2020, have been audited by Ernst & Young LLP, independent registered public accounting firm, as set forth in their reports thereon included therein, and incorporated herein by reference. Such financial statements are, and audited financial statements to be included in subsequently filed documents will be, incorporated herein in reliance upon the reports of Ernst & Young LLP pertaining to such financial statements and the effectiveness of our internal control over financial reporting as of the respective dates (to the extent covered by consents filed with the Securities and Exchange Commission) given on the authority of such firm as experts in accounting and auditing.

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ATI Inc.

$425,000,000 7.250% Senior Notes due 2030

P R O S P E C T U S   S U P P L E M E  N T

Book-Running Managers

Citigroup

Goldman Sachs & Co. LLC

J.P. Morgan

Co-Managers

BofA Securities

PNC Capital Markets LLC

MUFG

Wells Fargo Securities

HSBC

August 7, 2023