Comparison about effects of minor Zr, Sr and Ca additions on microstructure and tensile properties of Mg–5Gd–1.2Mn–0.4Sc (wt%) magnesium alloy

The effects of minor Zr, Sr and Ca additions on the microstructure and tensile properties of the as-cast and T5-treated Mg–5Gd–1.2Mn–0.4Sc (wt%) alloys were investigated and compared. The results indicate that adding 0.5 wt%Zr, 0.1 wt%Sr or 0.3 wt%Ca can refine the grains of the as-cast alloy. Among the three additions, the addition of 0.5 wt%Zr obtains the highest grain refining efficiency and followed by the additions of 0.3 wt%Ca and 0.1 wt%Sr, respectively. Furthermore, adding 0.3 wt%Ca is beneficial to the precipitation of Mg5Gd and Mn2Sc phases during T5 heat treatment of the alloy. In addition, adding 0.5 wt%Zr, 0.1 wt%Sr or 0.3 wt%Ca can also improve the tensile properties of the as-cast and T5-treated alloys. Among the three additions, the addition of 0.5 wt%Zr obtains the relatively highest tensile properties and followed by the additions of 0.3 wt%Ca and 0.1 wt%Sr, respectively.