Homogenization heat treatment of Mg–7.0 wt%Y–1.0 wt%Nd–0.5 wt%Zr alloy

Abstract

The microstructures and mechanical properties of Mg–7.0 wt%Y–1.0 wt%Nd–0.5 wt%Zr magnesium alloy were investigated both in as-cast condition and after homogenization heat treatment by differential scanning calorimetry (DSC), optical microscopy (OM), X-ray diffraction (XRD), scanning electron microscopy (SEM) and hardness measurement. The results indicate that the as-cast alloy consists of α-Mg matrix, Mg24Y5 and Mg41Nd5 phases, which are eutectic phases (cubic Y-rich phase). With the increase in homogenization temperature and time, the Mg24Y5 and Mg41Nd5 phases are completely dissolved into matrix, and only yttrium of intermetallic compounds leaves around boundary. After homogenization heat treatment, the elements distributed uniformly and the grains grow up not obviously, only yttrium element of intermetallic compounds left around boundary. The optimum homogenization condition is at 537 °C for 16 h. The mechanical properties are improved after homogenization, with tensile strength of σb = 181 MPa, yielding strength of σ0.2 = 144 MPa and elongation of δ = 5.5 %, which are better than those of as-cast alloy.