Microstructure and mechanical properties of as-cast and heat treated Mg-15Gd-3Y alloy

The microstructure evolution and mechanical properties of Mg-15Gd-3Y alloy were investigated in the as-cast and heat treated conditions. The microstructure evolution from as-cast to cast-T4 states involved alpha-Mg solid solution+Mg-5(Gd, Y) phase. alpha-Mg supersaturated solid solution+rare earths compound Mg-3(Gd-1.26, Y-0.74)->alpha-Mg supersaturated solid solution+rare earths compound Mg-3(Gd-0.745, Y-1.255). It showed that 480 degrees C/4 h was the optimal solution treatment parameter. If the solution temperature was high or the holding time was long, such as 520 degrees C/16 h, an overheating phenomenon would be induced, which had a detrimental effect on the mechanical properties. When ageing at 225 and 200 degrees C, the alloy would exhibit a significant age-hardening response and great long-time-age-hardening potential, respectively. The best mechanical properties were obtained at the parameters of 480 degrees C/4 h+225 degrees C/16 h, with the UTS of 257.0 MPa and elongation of 3.8%.