Effect of stress-aging treatment on the mechanical and corrosion properties of Al−Zn−Mg−Cu alloy

A stress-aging treatment (SAT) was applied to an Al−Zn−Mg−Cu alloy to obtain a good combination of strength and corrosion resistance. The effect of SAT on stress corrosion cracking (SCC), electrochemical corrosion, microstructure, and mechanical properties of Al−Zn−Mg−Cu alloy was investigated systematically using scanning electron microscopy (SEM), electron back-scattered diffraction (EBSD), transmission electron microscopy (TEM), slow strain rate tensile (SSRT), potentiodynamic polarization, etc. It was found that the number of matrix precipitates (MPs) under SAT increased and the size was reduced compared with that under stress-free aging treatment (SFAT). The MPs nucleated in large numbers due to the proliferation of dislocations caused by stress, and the alloy under SAT had a higher strength and earlier peak aging time than SFAT. In addition, large-sized and discontinuous grain boundary precipitates (GBPs) hindered the anodic dissolution of the grain boundaries (GBs) and the propagation of SCC, which improved the corrosion resistance of the alloy. This study has important guiding significance for rationally formulating the SAT process of Al−Zn−Mg−Cu alloys and improving alloy corrosion performance.