Homogenization heat treatment of Mg-7.68Gd-4.88Y-1.32Nd-0.63Al-0.05Zr alloy

The microstructures and mechanical properties of the Mg-7.68Gd-4.88Y-1.32Nd-0.63Al-0.05Zr magnesium alloy were investigated both in the as-cast condition and after homogenization heat treatment from 535 to 555 °C in the time range 0–48 h by optical microscopy, scanning electron microscopy and hardness measurement. The as-cast alloy consisted of α-Mg matrix, Mg₅(Y_0.5Gd_0.5) phase which is a eutectic phase, strip of Al₂(Y_0.6Gd_0.4) phase, little Al₃Zr and Mg(Y₃Gd) phase. With the increasing of homogenization temperature and time, the Mg₅(Y_0.5Gd_0.5) phase was completely dissolved into the matrix. The Al₂(Y_0.6Gd_0.4) phase was almost not dissolved which impeded grain boundaries motion making the grain size almost not changed in the process of homogenization. The optimum homogenization condition was 545 °C/16 h. The tensile strength increased, yield strength decreased and the plasticity improved obviously after 545 °C/16 h homogenization treatment.