Effects of minor Ca addition on as-cast microstructure and mechanical properties of Mg–4Y–1.2Mn–1Zn (wt.%) magnesium alloy

Highlights: •Minor Ca additions can refine the grains of the Mg–4Y–1.2Mn–1Zn alloy. •Minor Ca addition can improve the tensile properties of the Mg–4Y–1.2Mn–1Zn alloy. •Minor Ca addition can improve the creep properties of the Mg–4Y–1.2Mn–1Zn alloy. •Minor Ca addition can increase the thermal stability of the Mg12YZn phase. -- Abstract: The effects of minor Ca addition on the as-cast microstructure and mechanical properties of the Mg–4Y–1.2Mn–1Zn (wt.%) alloy were investigated by using optical and electron microscopies, differential scanning calorimetry (DSC) analysis, and tensile and creep tests. The results indicate that adding 0.3–0.9 wt.%Ca to the Mg–4Y–1.2Mn–1Zn alloy does not cause an obvious change in the morphology and distribution for the Mg12YZn phase in the alloy. However, the grains of the Ca-containing alloys are effectively refined, and an increase in Ca amount from 0.3 wt.% to 0.9 wt.% causes the grain size to gradually decrease. In addition, adding 0.3–0.9 wt.%Ca to the Mg–4Y–1.2Mn–1Zn alloy can effectively improve the tensile and creep properties. Among the Ca-containing alloys, the alloys with the additions of 0.6 and 0.9 wt.%Ca exhibit the relatively optimum tensile and creep properties. The improvement in the tensile and creep properties for the Ca-containing alloys is possibly related to the grain refinement and higher thermal stability of the Ca-containing Mg12YZn phases in the alloys, respectively