Microstructure evolution and mechanical properties of Mg-Gd-Sm-Zr alloys

The microstructure evolution and mechanical properties of Mg-Gd-Sm-Zr alloys during heat treatment were systematically investigated. The precipitation sequence of an α-Mg supersaturated solid solution (S.S.S.S., cph) during aging at 225 °C is: S.S.S.S.→β″ (D019)→β′ (cbco)→β1 (fcc)→β (fcc), which is different from previously reported Mg-Gd-Sm systems. The observed shortened incubation periods in the Mg-Gd-Sm-Zr alloys can be mainly attributed to the increased amount of Sm present. Peak-aged Mg-Gd-Sm-Zr alloys exhibit mechanical properties superior to that of the WE54 alloy. The product of strength and elongation (PSE) was used to estimate the toughness of Mg-Gd-Sm-Zr alloys, and the PSE value decreases with increasing RE content.