Structure, mechanical properties, and stress corrosion behaviour of high strength spray deposited 7000 series aluminium alloy

Abstract

A 7000 series high strength aluminium alloy was produced by spray deposition via the Osprey process. This alloy, designated AlZn11MgCu, exhibits an excellent combination of fracture toughness and strength in both the peak aged T6 and overaged T7 conditions. The yield strength and fracture toughness at room temperature are 700 MN m⁻² and about 40 MN m^−3/2 in the T6 temper, and 500 MN m⁻² and 75 MN m^−3/2 in the T7 temper, respectively. The exceptional high fracture toughness is attributed to the absence of coarse constituents and oxides. The microstructure is homogeneous, free of segregation, and has a fine grain size. The hardening precipitates in the T6 temper are mainly η′, and in the T7 temper they are η (MgZn₂), resulting in a different fracture behaviour; in the T6 temper the fracture mode is microshearing and in the T7 temper the fracture mode is ductile failure. Both T6 and T7 conditions show a stress corrosion crack growth rate higher than that of comparable alloys, 7075-T651 and 7075-T7351.

MST/1308