Effect of pre-strain and quench rate on stress corrosion cracking resistance of a low-Cu containing Al–Zn–Mg–Cu alloy

Abstract The synergy effect of quench rate and pre-strain prior to artificial aging heat treatment on microstructure, stress corrosion cracking (SCC) resistance, and mechanical property of a low-Cu containing Al–Zn–Mg–Cu alloy have been investigated using SCC and room temperature tensile tests, combined with X-ray diffraction, scanning electron microscopy (SEM), and high-angle angular dark-field scanning transmission electron microscopy (HAADF-STEM) microstructural examinations. The results showed that the SCC resistance was significantly improved by pre-strain and slow quench-rate owing to discontinuous distribution, large inter-space, and high Cu content of grain boundary precipitates. Moreover, the pre-strain was more effective for fast-quenched samples on improving SCC resistance compared with slowly quenched samples. The SCC mechanisms have been discussed in detail.