Patent ID: 8608876

Claim:
A method of manufacturing a wrought aluminium alloy product of an AA7000-series alloy, the method consisting of the following steps: a. casting stock of an ingot of an AA7000-series aluminium alloy having a chemical composition comprising, in wt. %: Zn about 6.4 to 10% Mg about 1 to 1.5% Cu 0.9 to about 2.5% Fe<0.25% Si≦0.12%, Mn<0.02%, balance being Al, incidental elements and impurities; b. preheating and/or homogenizing the cast stock at a temperature of less than 500° C.; c. heat treating the cast stock at a temperature in a range of more than 500° C. but lower than the solidus temperature of the subject aluminium alloy; d. hot working the stock by one or more methods selected from the group consisting of rolling and extruding; e. optionally cold working the hot-worked stock; f. first solution heat treating (SHT) of the hot-worked and optionally cold-worked stock, wherein the first solution heat treating is at a temperature and a time sufficient to place into solid solution soluble constituents in the aluminum alloy; g. second solution heat treating of the worked stock at a higher temperature than the first SHT the temperature being in a range of more than 500° C. but lower than the solidus temperature of the subject aluminium alloy in a time range of 2 to 180 minutes wherein the second SHT step dissolves Mg 2 Si in the alloy; h. cooling the SHT stock; i. stretching or compressing the cooled SHT stock or otherwise cold working the cooled SHT stock to release stresses; j. ageing the cooled and stretched or compressed or otherwise cold-worked SHT stock to achieve a desired temper.