X0306 4/A 2022-02-28 2022-03-02 0 0001018963 ALLEGHENY TECHNOLOGIES INC ATI 0001572385 WETHERBEE ROBERT S 1000 SIX PPG PLACE PITTSBURGH PA 15222 1 1 0 0 Board Chair, President and CEO Common Stock, par value $0.10 per share 2022-02-28 4 F 0 4453 25.70 D 380560.3409 D Shares withheld for payment of taxes on restricted stock units awarded in 2019. One-third of such restricted stock units vested by their terms on February 28, 2022. 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 28, 2022. This amended Form 4 is filed to reflect an administrative correction to the number of shares withheld for the payment of taxes with respect to the vesting of restricted stock units awarded in 2019, as reflected in Table I above. /s/ Elliot S. Davis, Attorney-in-Fact for Robert S. Wetherbee 2022-03-25