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v3.25.2

Debt Schedule of Debt (Details) - USD ($) $ in Millions | 6 Months Ended | 12 Months Ended |  |
--- | --- | --- | --- | ---
Jun. 29, 2025 | Dec. 29, 2024 | Jun. 13, 2025 | Jun. 12, 2025
Debt Instrument [Line Items] |  |  |  |
Debt Issuance Costs, Net | $ (12.9) | $ (14.2) |  |
Debt | 1,890.0 | 1,895.3 |  |
Short-term debt and current portion of long-term debt | 179.3 | 180.4 |  |
Long-term debt | 1,710.7 | 1,714.9 |  |
ATI Inc. 5.875% Notes due 2027 |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Debt, Gross | $ 350.0 | $ 350.0 |  |
Debt Instrument, Issuer | ATI Inc. | ATI Inc. |  |
Interest rate | 5.875% | 5.875% |  |
Allegheny Ludlum 6.95% Debentures due 2025 (a) |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Debt, Gross | $ 150.0 | $ 150.0 |  |
Debt Instrument, Issuer | Allegheny Ludlum | Allegheny Ludlum |  |
Interest rate | 6.95% | 6.95% |  |
Foreign credit facilities |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Short-term Debt | $ 0.0 | $ 0.0 |  |
Finance leases and other |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Debt, Gross | 102.9 | 109.5 |  |
ATI 2031 Notes |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Debt, Gross | $ 350.0 | $ 350.0 |  |
Debt Instrument, Issuer | ATI Inc. | ATI Inc. |  |
Interest rate | 5.125% | 5.125% |  |
ATI 2029 Notes |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Debt, Gross | $ 325.0 | $ 325.0 |  |
Debt Instrument, Issuer | ATI Inc. | ATI Inc. |  |
Interest rate | 4.875% | 4.875% |  |
Domestic Bank Group $600 million asset-based credit facility |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Short-term Debt | $ 0.0 | $ 0.0 |  |
ATI 2030 Notes |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Debt, Gross | $ 425.0 | $ 425.0 |  |
Debt Instrument, Issuer | ATI Inc. | ATI Inc. |  |
Interest rate | 7.25% | 7.25% |  |
2030 Term Loan |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Debt, Gross | $ 200.0 | $ 200.0 |  |
Revolving credit facility | Domestic Bank Group $600 million asset-based credit facility |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Debt Issuance Costs, Net |  |  | $ (2.8) | $ (1.9)

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