Evolution of Microstructure and Mechanical Properties in Al–Zn–Mg–Cu Alloy by Electric Pulse Aging Treatment

In this study, a new green rapid aging treatment method was explored, namely electric pulse aging treatment (EPAT). The effect of rapid aging treatment on the microstructure of the alloy was investigated by SEM, XRD and HRTEM. The results show that the as-cast alloy is mainly composed of many gray-white non-equilibrium eutectic phases and α-Al, and there is serious segregation in the grain boundaries. The Zn, Cu and Mg elements dissolve into α-Al matrix to form supersaturated solid solution when the alloy is treated with solid solution at 470 °C for 2 h. The small second phase particles gradually disappear in the matrix, while the larger second phases are less dissolved into the matrix. It can be seen that the tensile strength and elongation of the alloy experiencing EPAT are significantly improved. The tensile strength and elongation of the alloy after EPAT for 4 h are 14.1 MPa and 4.45% higher than that of conventional heat treatment, respectively. The most important thing is that, the aging time is shortened by 12 h, which can effectively save energy. It provides a new method and theoretical basis for obtaining good mechanical properties and industrial application of Al–Zn–Mg–Cu alloy.