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(Y0.5Gd0.5) phase which is a eutectic phase, strip of Al2(Y0.6Gd0.4) phase, little Al3Zr and Mg(Y3Gd) phase. With the increasing of homogenization temperature and time, the Mg5(Y0.5Gd0.5) phase was completely dissolved into the matrix. The Al2(Y0.6Gd0.4) 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.