Filed by Alcoa Inc.

Pursuant to Rule 425 under the Securities Act of 1933

and deemed filed pursuant to Rule 14a-12

of the Securities Exchange Act of 1934

Subject Company: RTI International Metals, Inc.

Commission File No.: 001-14437

On March 9, 2015, the following letter from Dawne S. Hickton, Vice Chair, President, and Chief Executive Officer of RTI International Metals, Inc. (“RTI”), was posted on a Web site of Alcoa Inc. created for use by RTI employees.

Dear RTI Employees,

Nothing is more constant in business than change. The purpose of this letter is to brief you on an historic change for RTI. This morning, we announced that RTI has entered into a definitive agreement to be acquired by Alcoa, a company with $24 billion in revenue in 2014 and a more than 125-year history, as part of a $1.5 billion deal.

As a public company, with our ownership shares traded on the New York Stock Exchange, RTI’s strategic plan directs us to maximize value for our shareholders – a group that includes many of you. This transaction will do that by delivering significant, immediate value, as well as long-term growth, to our shareholders. Under terms of the agreement, Alcoa will acquire all outstanding shares of RTI in a stock-for-stock transaction where RTI shareholders will receive 2.8315 Alcoa shares for each RTI share, representing a value of $41 per RTI share based on Alcoa’s closing price on March 6, 2015.

This transaction is a great fit for our companies, customers and employees. Fortune magazine has named Alcoa the most admired metals company four years in a row, and its recent acquisitions of Firth Rixson, TITAL, and now RTI are part of Alcoa’s transformation from an aluminum company to a lightweight, multi-material innovator. With RTI, Alcoa will grow its value-add business, strengthen its aerospace and energy portfolios, diversify its markets with the addition of medical, and expand its range of titanium offerings and advanced additive manufacturing technologies. In return, RTI gains greater depth of capital and resources to further innovation and enhance our vertical integration strategy across our business and our supply chain.

Beyond that, this transaction will bring opportunities for RTI’s Dynamic Workforce. As a part of that workforce, you have played an important role in building RTI’s Valued Brand over the years. Today, Alcoa’s offer confirms that value and promises additional resources and opportunities that will drive workforce development and the creation of an even brighter future for employees.

In the near term it is important that we focus on delivering the same quality, service and financial performance that we outlined in our 2015 operating plan. We will continue to do “business as usual” and remain focused on driving our strategic initiatives. RTI’s bonus plan provides for a quarterly payment based on achievement of our operating plan targets. These payments should serve as a retention incentive and a motivator to continue running our business to our usual standards of excellence.

Please understand that this transaction will not be finalized immediately, nor can we communicate all details immediately. We must wait for shareholder and regulatory approvals and other legal requirements to be met –something we are working diligently to accomplish. Rest assured that you will receive regular updates regarding the status of the process through its closing, which we anticipate to occur in the next three to six months.

A press release regarding this transaction is attached, along with an introductory letter from Klaus Kleinfeld, Chairman and CEO of Alcoa. Please take some time to read both of them. After

that, I invite you to join me on a global employee webcast at 11:00 am EST this morning to hear in greater detail why our two companies are a great fit. You will receive separate communication via email or from your supervisor about how to join this webcast.

Thank you for all that you do to make RTI a success.

Sincerely,

Dawne S. Hickton

Vice Chair, President and CEO

“Safe Harbor” Statement under the Private Securities Litigation Reform Act of 1995

This communication contains “forward-looking” statements within the meaning of Section 21E of the Securities Exchange Act of 1934, as amended, and the Private Securities Litigation Reform Act of 1995, known as the PSLRA. These statements, as they relate to RTI and Alcoa, the management of either such company or the proposed transaction between RTI and Alcoa, involve risks and uncertainties that may cause results to differ materially from those set forth in the statements. These statements are based on current plans, estimates and projections, and therefore, you are cautioned not to place undue reliance on them. No forward-looking statement can be guaranteed, and actual results may differ materially from those projected. RTI and Alcoa undertake no obligation to publicly update any forward-looking statement, whether as a result of new information, future events or otherwise, except to the extent required by law. Forward-looking statements are not historical facts, but rather are based on current expectations, estimates, assumptions and projections about the business and future financial results, and other legal, regulatory and economic developments. We use words such as “anticipates,” “believes,” “plans,” “expects,” “projects,” “future,” “intends,” “may,” “will,” “should,” “could,” “estimates,” “predicts,” “potential,” “continue,” “guidance,” and similar expressions to identify these forward-looking statements that are intended to be covered by the safe harbor provisions of the PSLRA. Actual results could differ materially from the results contemplated by these forward-looking statements due to a number of factors, including: the risk that the businesses will not be integrated successfully; the risk that the cost savings and any other synergies from the transaction may not be fully realized or may take longer to realize than expected; restrictions imposed by outstanding indebtedness; worldwide and regional economic, business, and political conditions; changes in customer demand and requirements; business cycles and other industry conditions; the timing of new services or facilities; ability to compete with others in the industries in which RTI and Alcoa operate; effects of compliance with laws; fluctuations in the value of currencies in major areas where operations are located; matters relating to operating facilities; effect and costs of claims (known or unknown) relating to litigation and environmental remediation; ability to develop and further enhance technology and proprietary knowhow; ability to attract and retain key personnel; escalation in the cost of providing employee health care; disruption from the transaction making it more difficult to maintain relationships with customers, employees or suppliers; the failure to obtain governmental approvals of the transaction on the proposed terms and schedule, and any conditions imposed on the combined company in connection with consummation of the merger; the failure to obtain approval of the merger by the requisite vote of the shareholders of RTI and the failure to satisfy various other conditions to the closing of the merger contemplated by the merger agreement; and the risks that are described from time to time in RTI’s and Alcoa’s respective reports filed with the SEC, including RTI’s annual report on Form 10-K for the year

ended December 31, 2014 and Alcoa’s annual report on Form 10-K for the year ended December 31, 2014, in each case, as such reports may have been amended. This document speaks only as of its date, and RTI and Alcoa each disclaims any duty to update the information herein.

Additional Information and Where to Find It

In connection with the proposed transaction, a registration statement on Form S-4 will be filed with the SEC. RTI SHAREHOLDERS ARE ENCOURAGED TO READ THE REGISTRATION STATEMENT AND ANY OTHER RELEVANT DOCUMENTS FILED WITH THE SEC, INCLUDING THE PROXY STATEMENT/PROSPECTUS THAT WILL BE PART OF THE REGISTRATION STATEMENT, WHEN THEY BECOME AVAILABLE, BECAUSE THEY WILL CONTAIN IMPORTANT INFORMATION ABOUT THE PROPOSED MERGER. The final proxy statement/prospectus will be mailed to shareholders of RTI. Investors and security holders will be able to obtain the documents free of charge at the SEC’s website, www.sec.gov, from Alcoa at its website, www.alcoa.com, or 390 Park Avenue, New York, NY 10022, attention: Corporate Secretary, or from RTI at its website, www.rtiintl.com, or Westpointe Corporate Center One, 1550 Coraopolis Heights Rd, Pittsburgh, PA 15108, attention: Secretary.

Participants In Solicitation

RTI and Alcoa and their respective directors and executive officers and other members of management and employees may be deemed to be participants in the solicitation of proxies in respect of the proposed merger. Information concerning RTI’s participants is set forth in the proxy statement, dated March 28, 2014, for RTI’s 2014 annual meeting of shareholders as filed with the SEC on Schedule 14A. Information concerning Alcoa’s participants is set forth in the proxy statement, dated March 18, 2014, for Alcoa’s 2014 annual meeting of shareholders as filed with the SEC on Schedule 14A. Additional information regarding the interests of participants of RTI and Alcoa in the solicitation of proxies in respect of the proposed merger will be included in the registration statement and proxy statement/prospectus and other relevant materials to be filed with the SEC when they become available.

This communication shall not constitute an offer to sell or the solicitation of an offer to sell or the solicitation of an offer to buy any securities, nor shall there be any sale of securities in any jurisdiction in which such offer, solicitation or sale would be unlawful prior to registration or qualification under the securities laws of any such jurisdiction. No offer of securities shall be made except by means of a prospectus meeting the requirements of Section 10 of the Securities Act of 1933, as amended.

Forward-Looking Statements

Certain statements in this report, including statements regarding the proposed acquisition of RTI by Alcoa, the expected timing, closing and benefits of the transaction, the expected synergies, the expected contribution of RTI to Alcoa’s revenues and profitability, the expected acceleration of Alcoa’s portfolio transformation, the expected size, scope and growth of the combined company’s operations and the markets in which it will operate, including the aerospace market, the anticipated issuance of Alcoa common stock in exchange for RTI stock in the transaction, as well as Alcoa’s plans, objectives, strategy, and intentions, may contain words such as “anticipates,” “believes,” “could,” “estimates,” “expects,” “forecasts,” “intends,” “may,” “outlook,” “plans,” “projects,” “seeks,” “sees,” “should,” “targets,” “will,” or other words of similar meaning that constitute forward-looking statements within the meaning of the Private Securities Litigation Reform Act of 1995. These statements are based on Alcoa’s current expectations, estimates, forecasts and projections about the proposed transaction and the operating environment, economies and markets in which Alcoa and RTI operate. In making these statements, Alcoa has made assumptions with respect to: the ability of Alcoa and RTI to achieve expected synergies and the timing of same; the ability of Alcoa and RTI to predict and adapt to changing customer requirements, demand, and preferences; future capital expenditures, including the amount and nature thereof; trends and developments in the aerospace, metals engineering (including aluminum and titanium), advanced manufacturing, and other sectors of the economy that are related to these sectors; business strategy and outlook; expansion and growth of business and operations; credit risks; future results being similar to historical results; expectations related to future general economic and market conditions; and other matters, many of which are beyond Alcoa’s control. Alcoa’s beliefs and assumptions are inherently subject to significant business, economic, competitive and other uncertainties and contingencies regarding future events and as such, are subject to change and may prove to be inaccurate. Actual results or events could differ materially from those contemplated in forward-looking statements as a result of numerous risks and uncertainties, including: (a) the risk that the businesses will not be integrated successfully or such integration may be more difficult, time-consuming or costly than expected, which could result in additional demands on Alcoa’s resources, systems, procedures and controls, disruption of its ongoing business and diversion of management’s attention from other business concerns; (b) the effect of an increased number of Alcoa shares outstanding as a result of the proposed transaction; (c) the possibility that certain assumptions with respect to RTI or the proposed transaction could prove to be inaccurate; (d) failure to receive the required votes of RTI’s shareholders to approve the transaction; (e) failure to receive, delays in the receipt of, or unacceptable or burdensome conditions imposed in connection with, all required regulatory approvals of the proposed transaction, or the failure to satisfy the other closing conditions to the proposed transaction; (f) the potential failure to retain key employees of Alcoa or RTI as a result of the proposed transaction or during integration of the businesses; (g) potential sales of Alcoa common stock issued in the acquisition; (h) the potential loss of customers, suppliers, and other business relationships of Alcoa or RTI as a result of the transaction; (i) consequences of investigations by governmental agencies or regulatory authorities; (j) the failure to capitalize on anticipated growth in the commercial aerospace market; and (k) the other risk factors summarized in Alcoa’s Form 10-K for the year ended December 31, 2014, and other reports filed with the Securities and Exchange Commission. Alcoa disclaims any obligation to update publicly any forward-looking statements, whether in response to new information, future events or otherwise, except as required by applicable law. Market projections are subject to the risks discussed above and other risks in the market. Nothing on Alcoa’s website is included or incorporated by reference herein.

Additional Information and Where to Find It

This document does not constitute an offer to sell or the solicitation of an offer to buy any securities or a solicitation of any vote or approval nor shall there be any sale of securities in any jurisdiction in which such offer, solicitation or sale would be unlawful prior to registration or qualification under the securities laws of any such jurisdiction. The proposed business combination transaction between Alcoa and RTI will be submitted to the shareholders of RTI for their consideration. Alcoa will file with the Securities and Exchange Commission (the “SEC”) a Registration Statement on Form S-4 that will include a proxy statement of RTI that also constitutes a prospectus of Alcoa. RTI will provide the proxy statement/prospectus to its shareholders. Alcoa and RTI also plan to file other documents with the SEC regarding the proposed transaction. This document is not a substitute for any prospectus, proxy statement or any other document which Alcoa or RTI may file with the SEC in connection with the proposed transaction. INVESTORS AND SECURITY HOLDERS OF RTI ARE URGED TO READ THE PROXY STATEMENT/PROSPECTUS AND ANY OTHER RELEVANT DOCUMENTS THAT WILL BE FILED WITH THE SEC CAREFULLY AND IN THEIR ENTIRETY WHEN THEY BECOME AVAILABLE BECAUSE THEY WILL CONTAIN IMPORTANT INFORMATION ABOUT THE PROPOSED TRANSACTION. You may obtain copies of all documents filed with the SEC regarding this transaction, free of charge, at the SEC’s website (www.sec.gov). You may also obtain these documents, free of charge, from both Alcoa’s website (www.alcoa.com) and RTI’s website (www.rtiintl.com).

Participants in the Solicitation

Alcoa, RTI, and certain of their respective directors, executive officers and other members of management and employees may be deemed to be participants in the solicitation of proxies from RTI shareholders in connection with the proposed transaction. Information regarding the persons who may, under the rules of the SEC, be deemed participants in the solicitation of RTI shareholders in connection with the proposed transaction will be set forth in the proxy statement/prospectus when it is filed with the SEC. You can find information about Alcoa’s executive officers and directors in its definitive proxy statement filed with the SEC on March 18, 2014 and in its Annual Report on Form 10-K filed with the SEC on February 19, 2015. You can find information about RTI’s executive officers and directors in its definitive proxy statement filed with the SEC on March 28, 2014 and in its Annual Report on Form 10-K filed with the SEC on February 26, 2015. Additional information about Alcoa’s executive officers and directors and RTI’s executive officers and directors can be found in the above-referenced Registration Statement on Form S-4 when it becomes available. You can obtain free copies of these documents from Alcoa and RTI as described in the preceding paragraph.