Patent ID: 7883591

Claim:
Method for producing a high strength, high toughness Al—Zn alloy product with good corrosion resistance, consisting of the sequential steps of: a) casting an ingot with the following composition, in weight percent: Zn 6.0 to 11.0% Cu 1.4 to 2.2% Mg 1.4 to 2.4% Zr 0.05 to 0.15% Ti <0.05% Hf and/or V <0.25%, optionally Sc and/or Ce 0.05 to 0.25%, optionally Mn 0.05 to 0.12%, and inevitable impurities and balance aluminium, b) homogenising or pre-heating the ingot after casting, c) in a first hot rolling step, hot rolling the homogenised or pre-heated ingot into a pre-worked product, d) reheating the pre-worked product, and then in a second hot rolling step hot rolling the reheated product to a thickness in a range selected from the group consisting of about 150 to 250 (in final-gauge %) or about 105 to 140 (in final-gauge %) at low temperatures in the range of 300° C. to 420° C. to prevent the alloy product from recrystallising and then, after the second hot rolling step, cold rolling the reheated product to a final gauge, wherein the final gauge has a thickness of from 4 to 60 mm, e) solution heat-treating the cold-rolled product and quenching the solution heat-treated product, f) optionally stretching or compressing of the quenched alloy product, g) artificially ageing the reheated, hot- and cold-rolled, solution heat-treated, quenched and optionally stretched or compressed alloy product by a two-step ageing treatment to produce the alloy product to have a T79 or T76 temper, wherein the first ageing step is at a temperature in a range of 105 to 135° C. for 2 to 20 hours and the second ageing step is at a temperature higher than 135° C. but less than 210° C. for 4 to 12 hours to a temper selected from T79 and T76 temper, and wherein more than 80% of the gauge of the artificially aged alloy product has a substantially unrecrystallised microstructure.