Influence of trace Sr additions on the microstructures and the mechanical properties of Mg–Al–La-based alloy

Abstract The microstructure, tensile properties and creep behavior of the high-pressure die-cast Mg–4Al–4La– x Sr ( x =0, 0.12, 0.25, 0.50, wt%) alloys were thoroughly studied. First, the eutectic morphologies change drastically after trace Sr addition, with some Al 11 La 3 particles becoming plate and their distributions being irregular to some extent. This is probably due to Al 4 Sr particles that act as the nucleation substrates for Al 11 La 3 phase during solidification. Second, the tensile properties of ALa44 alloy are distinctly improved by trace Sr addition. For instance, the yield strength, ultimate tensile strength, and elongation at 150 °C are improved by 13%, 10%, and 16%, respectively, after 0.25 wt% Sr addition. Third, the influence of trace Sr addition on the creep behavior of ALa44 alloy is complicated that the creep resistance is slightly improved at 200 °C and 75 MPa, but it is deteriorated after trace Sr addition at 200 °C and 85 MPa. Finally, the underlying causes of the complicated creep behavior and the operative creep mechanisms for the studied alloys are analyzed and discussed based on TEM observations.