Tailoring precipitates in Mg–12Gd-3Y alloys by Sn addition to obtain superior elevated temperature mechanical properties

The precipitation phase was tailored by adding different Sn contents to the Mg-12Gd-3Y alloy to achieve multiphase composite strengthening. Adding different Sn contents has different effects on the microstructure and mechanical properties. Adding 1.0 wt% Sn to the Mg-12Gd-3Y alloy produced Mg5RE, Sn3RE5, and β′ precipitates, which were uniformly diffusely distributed within the alloy. When Sn elements were added up to 1.5 wt%, Mg5RE and Sn3RE5 precipitates increased and aggregated into lumps. The prepared Mg-12Gd-3Y-1.0Sn alloy exhibited excellent room and elevated temperature (ET) mechanical properties. The ultimate tensile strengths (UTS) of Mg-12Gd-3Y-1.0Sn alloy after extrusion and aging (E-A) treatment were 476, 415, 383 MPa at RT, 200 °C, and 250 °C, respectively. The fine grain size inhibits dislocation sliding, and the uniformly diffuse multi-scale phase structure inhibits the expansion of grain boundary cracks, resulting in excellent strength of Mg-12Gd-3Y-1.0Sn at room temperature (RT). The excellent ET strength of the Mg-12Gd-3Y-1.0Sn alloy is derived from the homogeneous diffusion of multi-scale heat-resistant precipitates within the alloy.