Patent ID: 11879166
Assignee: NOVELIS KOBLENZ GMBH
Field: Materials, metallurgy (Chemistry)
Classification: CPC C | IPC C

Claim 0:
1. A wrought 7xxx-series aluminium alloy product having a composition comprising, in wt. %,
Zn 6.40 to 6.60,
Mg 2.25 to 2.60,
Cu 1.50 to 1.80,
and wherein Cu+Mg<4.50, and wherein Mg<2.5+5/3(Cu−1.2),
Fe up to 0.05,
Si up to 0.05, and
optionally one or more elements selected from the group consisting of:
Zr up to 0.3,
Cr up to 0.3,
Ti up to 0.05,
Sc up to 0.05,
Ag up to 0.05,

a balance being aluminium and impurities, wherein the composition is free from Mn, wherein said wrought 7xxx-series aluminium alloy product is aged to achieve:
a minimum life without failure due to stress corrosion cracking (SCC) measured in accordance with ASTM G47-98 of at least 30 days, at a short transverse (ST) stress level of 170 MPa; and
a minimum life without failure due to environmental assisted cracking (EAC) in a sodium chloride free humid atmosphere and measured with constant load testing configurations in accordance with ASTM G47-98 on round ST tension specimens of at least 50 days at a short transverse (ST) constant load stress level of 85% Yield Strength (YS), and with a continuous exposure to a temperature of 70° C., and at a humidity of 85% (RH).