Mechanical properties of solution heat treated Al-Zn-Mg-Cu (7075) alloy under different cooling conditions: analysis with full field measurement and finite element modeling

Abstract The effect of W-temper heat treatment, consisting of solution heat treatment (SHT) and rapid cooling, on the mechanical properties and fracture of high strength aluminum alloy 7075 sheet is investigated experimentally and numerically. Three different cooling conditions from the solution heat treated as-received T6 temper 7075 alloy sheet are considered: water quenching, die quenching, and air cooling. The mechanical properties are measured by uniaxial tensile tests and limiting dome height (LDH) formability tests on the heat treated samples. Moreover, the distributions of strain and strain rate are analyzed by the full-field digital image correlation (DIC) technique, which enables the quantitative investigation on the Portevin–Le Chatelier (PLC) band propagations induced by dynamic strain aging (DSA). The DIC analysis reveals the distinctive formability between uniaxial and biaxial tensile stress states of the W-temper samples. In the finite element analysis, the hardening model based on Kocks-Mecking-Estrin-McCormick (KMEC) model is employed to incorporate the DSA-originated PLC band propagation in the simulation of LDH formability test. The simulated LDHs agree well with experiments when the PLC effect along with planar anisotropy of the heat treated 7075 alloy sheets is properly implemented.