X0306 4 2021-02-22 0 0001018963 ALLEGHENY TECHNOLOGIES INC ATI 0001332656 Powers Elizabeth C 1000 SIX PPG PLACE PITTSBURGH PA 15222 0 1 0 0 Senior VP, CHRO Common Stock, par value $0.10 per share 2021-02-22 4 F 0 1520 19.89 D 147070.8867 D Shares withheld for payment of taxes on restricted stock units awarded on February 20, 2018. One-third of such restricted stock units vested by their terms on February 22, 2021. Represents the average of the high and low trading prices for one share of the Issuer's common stock on the New York Stock Exchange on February 22, 2021. This amount includes 1,919.0802 shares of common stock that Ms. Powers owns in the Company's 401(k) Plan. Fluctuations in 401(k) share amounts reflect the Plan's unit reporting method. Ms. Powers holds approximately 1,610 units, which represent interests in the Company's stock fund. /s/ Elliot S. Davis, Attorney-in-Fact for Elizabeth C. Powers 2021-02-24