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

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.