Effects of stress aging treatment on the microstructure, mechanical properties and electrochemical corrosion behavior of Al-Zn-Mg-Cu alloy

This paper aims to investigate the effects of stress aging treatment on the microstructure, mechanical properties and corrosion behavior of Al-Zn-Mg-Cu alloy. The alloys were subjected to SAT and stress-free aging treatment (SFAT) at 175 °C under different aging stress and aging time conditions. Various analytical techniques, including scanning electron microscopy (SEM), electron back-scatter diffraction (EBSD), transmission electron microscopy (TEM), slow strain rate tensile, X-ray Diffraction (XRD) and potentiodynamic polarization, were employed to obtain results. The findings demonstrate heightened strength, improved corrosion resistance under SAT conditions in contrast to SFAT. The alloys subjected to SAT exhibit higher strength compared to SFAT, attributed to the diffusion of stress-induced dislocations and extensive nucleation of matrix precipitates. Furthermore, the presence of large-sized and discontinuous grain boundary precipitates impedes the anodic dissolution of grain boundaries and the expansion of stress corrosion, contributing to the enhanced corrosion resistance of the alloy. •The strength of the alloys showed an increasing and then decreasing trend with increasing applied stress, the correct application of SAT can improve the strength of alloys.•SAT results in lower Icorr values compared to SFAT. S100 exhibits a larger capacitance arc in the Nyquist plots, indicative of superior corrosion resistance.•SAT improves the mechanical properties of the alloy. Applied stress facilitates dislocation diffusion and aggregation, creating additional nucleation sites that promote the nucleation and growth of precipitated phases.•SAT improves the corrosion resistance of the alloy. Applying aging stress beyond a specific threshold and extending the aging time both facilitated Gbps growth and widened the PFZ. Thereby enhancing the alloy's corrosion resistance.