Influencing mechanisms of heat treatments on microstructure and comprehensive properties of Al–Zn–Mg–Cu alloy formed by spray forming

In this research, the effects of solid solution, peak aging (PA), over aging (OA) and retrogression re-aging (RRA) on microstructure, mechanical properties, and corrosion resistance of the spray-formed Al–Zn–Mg–Cu alloy were systematically and comparatively studied. It was found that after solid solution, most of the secondary phases dissolved into the α(Al) matrix and created a favorable condition for aging treatment. When the material was subjected to the RRA, the microstructure of the alloy consisted of fine precipitates within the grains similar to the PA condition and discontinuous coarse precipitates along the grain boundaries resembling the OA condition, allowing the RRA specimens to possess optimal strength (747MPa) and high intergranular corrosion (IGC) resistance. The mechanism of IGC on mechanical properties on different aged samples was elaborated.