| 摘要 |
PROBLEM TO BE SOLVED: To improve grain boundary corrosion resistance and stress corrosion resistance, etc., even in the case of containing Cu, by arranging a hydrate-oxide film of Al having the specified thickness on the surface of a cast and forged material. SOLUTION: The thickness of the hydrate-oxide film of Al arranged on the surface of the Al alloy is made to 100-800Å. The Al alloy to be applied, contains >=0.05% Cu, and has desirably >=280 N/mm2 the average value of proof stress (σ0.2) in artificial aging-hardening treatment, >=20 J/cm2 the average value of Charpy impact value as the forged material. Further, the alloy has desirably >=230 N/mm2 the average value of theσ0.2>=12 J/cm2 the average value of Charpy impact value and >=18% elongation as the cast material. For satisfying the characteristics, as the forged material, the Al alloy is desirable to contain, by mass %, 0.6-1.6% Mg and 0.8-1.8% Si. Further, as the cast material, the Al alloy is desirable to contain 2.0% Si and cast with a high pressure casting method and to be the one applied with a solution heat treatment and the artificial aging-hardening treatment.
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