Al—Zn—Mg—Cu alloy with improved damage tolerance-strength combination properties

Method of producing a high-strength, high-toughness AA7xxx-series alloy product having a good corrosion resistance, comprising the processing steps of:

• a) casting an ingot having a composition comprising, in wt. %:
• Zn 6.9 to 7.9
• Mg 1.4 to 2.1
• Cu 1.43 to 1.90
• Zr up to 0.15
• Ti<0.05
• Fe<0.05
• Si<0.07
• Mn 0.15 to 0.30,
• Cr 0.15 to 0.20
• and other impurities or incidental elements each <0.05, total <0.15, and the balance being aluminium;
• b) homogenizing the ingot after casting in a range of 460° C. to 490° C., then cooling the homogenized ingot, and then homogenizing the cooled ingot to a temperature in a range of 460° C. to 490° C.;
• c) hot working the homogenized ingot by hot rolling to a desired workpiece form, wherein said hot working the homogenized ingot is by said hot rolling with an absence of forging and an absence of extrusion;
• d) solution heat treating said formed workpiece at a temperature and time sufficient to place into solid solution essentially all soluble constituents in the alloy;
• e) quenching the solution heat treated workpiece by one of spray quenching or immersion quenching in water or other quenching media;
• f) stretching of the quenched workpiece at most 8%;
• i) artificially ageing the quenched and stretched workpiece in a two step ageing procedure to achieve a temper selected from the group consisting of T74, T76, T751, T7451, T7651, T77 and T79, wherein the artificial ageing comprises a first ageing step at a temperature in a range of 105° C. to 135° C. for 2 to 20 hours and a second ageing step at a temperature in a range of 135° C. to 210° C. for 4 to 20 hours,
• wherein the product has a thickness of 2.5 to 11 inches.