X0306 4 2023-01-03 0 0001018963 ATI INC ATI 0001776844 Harris Timothy J C/O ALLEGHENY TECHNOLOGIES INCORPORATED 1000 SIC PPG PLACE PITTSBURGH PA 15222 0 1 0 0 Senior VP and CDIO Common Stock, par value $0.10 per share 2023-01-03 4 A 0 10148 0.00 A 95435 D Common Stock, par value $0.10 per share 2023-01-04 4 F 0 5701 30.38 D 88734 D Common Stock, par value $0.10 per share 2023-01-04 4 F 0 3279 30.38 D 86455 D Award of restricted stock units, which are settled in shares of stock upon vesting. The award vests in three equal annual installments on each of the first three anniversaries of the grant date. Awarded under ATI's 2022 Incentive Plan. Shares withheld for payment of taxes on restricted stock units awarded on January 4, 2021. One-third of such restricted stock units vested by their terms on January 4, 2023. 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 ("NYSE") on January 4, 2023. Shares withheld for payment of taxes on restricted stock units awarded on January 4, 2022. One-third of such restricted stock units vested by their terms on January 4, 2023. /s/ Amanda J. Skov, Attorney-in-Fact for Timothy J. Harris 2023-01-05