Microstructure and high-temperature mechanical properties of the Mg-4Zn-0.5Ca alloy in the as-cast and aged conditions

Shear punch test (SPT) was employed to study the high temperature mechanical properties of an Mg-4Zn-0.5Ca (wt%) alloy in the as-cast and aged conditions in the temperature range 150-250 °C. The microstructure of the as-cast alloy consisted of α-Mg matrix with some Ca2Mg6Zn3 and MgZn second phase particles distributed in the interdendritic regions. Aging treatment resulted in the formation of equiaxed α-Mg grains together with coarse Ca2Mg6Zn3 phase in the form of a semi-continuous network at the grain boundaries and triple points, while nano-sized Mg4Zn7, MgZn2, and Ca2Mg6Zn3 precipitates formed in the grain interiors. These phases have high thermal stabilities that could improve the high-temperature mechanical properties of the tested alloy after aging treatment.