X0508 4 2024-01-03 0 0001018963 ATI INC ATI 0001520037 Davis Elliot S C/O ATI INC. 2021 MCKINNEY AVE., SUITE 1100 DALLAS TX 75201 0 1 0 0 Chief Legal & Compl. Officer 0 Common Stock, par value $0.10 per share 2024-01-03 4 A 0 7229 0.00 A 148855.6389 D Common Stock, par value $0.10 per share 2024-01-03 4 F 0 1699 43.19 D 147156.6389 D Common Stock, par value $0.10 per share 2024-01-04 4 F 0 9321 43.56 D 137835.6389 D Common Stock, par value $0.10 per share 2024-01-04 4 S 0 1789 43.06 D 136049.6389 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 the payment of taxes on restricted stock units that vested on January 3, 2024. 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 January 3, 2024. Shares withheld for the payment of taxes on restricted stock units that vested on January 4, 2024. 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 January 4, 2024. Shares sold pursuant to a 10b5-1 Trading Plan. /s/ Elliot S. Davis 2024-01-05