Effect of heat treatments on mechanical properties and corrosion behavior of MgY₃Zn₂Al magnesium alloy

MgY₃Zn₂Al alloy with long-period stacking ordered (LPSO) phase was prepared by conventional casting method, and then was T4 heat treated at 400, 430 and 460 °C. The optical microscopy (OM), X-ray diffraction (XRD) and the scanning electron microscope (SEM) equipped with energy dispersive X-ray spectroscopy (EDS) were used to analyze the microstructure of the alloy after heat treated at different temperature. Tensile tests were used to evaluate the mechanical properties of the alloy. The immersion and electrochemical experiments with 3.5% NaCl solution were used to evaluate the corrosion behavior of the alloy. The results showed that the amount of grain boundary LPSO phase decreased with increasing of the heat treatment temperature. The plasticity of MgY₃Zn₂Al alloy after heat treatment is significantly increased compared with that of as-cast state, and appropriate heat treatment temperature can increase the strength of the alloy. The corrosion resistance of the alloy was the best at as-cast state, while heat treatment could decrease the corrosion resistance of the alloy apparently. (paper)