A 7XXX series aluminum
alloy having reduced quench sensitivity suitable for use in
aerospace structural components, such as integral wing spars, ribs, extrusions and forgings comprises, in weight %: 6 to 10 Zn, 1.3 to 1.9 Mg, 1.4 to 2.2 Cu, wherein Mg<=Cu+0.3, one or more of 0 to 0.4 Zr, up to 0.4 Sc, up to 0.2 Hf, up to 0.4 Cr, up to 1.0 Mn and the balance Al plus incidental additions including Si, Fe, Ti and the like plus impurities. By controlling the Mg content to 1.3 to 1.7 wt. %, limiting Mg<=Cu+0.3 and 6.5<=Zn<=8.5, the
alloy provides significantly improved combined strength and
fracture toughness in heavy gauges. For example, in a six-inch
thick plate there is provided a combination of about 75 ksi quarter-plane tensile yield strength (L) with a
fracture toughness (L-T) of about 33 ksi{square root}in which progresses by
artificial aging /
tempering to a combined strength and
fracture toughness of about 67 ksi tensile yield strength (L) and a fracture
toughness (L-T) of about 40 ksi{square root}in. The
alloy product possesses equally attractive combinations of strength and fracture
toughness when intentionally quenched slowly following solution heat treatment so as to lessen dimensional
distortion, particularly in shapes of varying cross section.