As-cast microstructures and mechanical properties of Mg-4Zn-xY-1Ca (x=1.0, 1.5, 2.0, 3.0) magnesium alloys

The as-cast microstructures and mechanical properties of Mg-4Zn-xY-1Ca (x=1.0, 1.5, 2.0 and 3.0, mass fraction, %) alloys were investigated and compared. The results indicate that all the as-cast alloys are mainly composed of α-Mg, Mg2Ca, Ca2Mg6Zn3, I (Mg3YZn6) and W (Mg3Y2Zn3) phases. However, with Y content increasing from 0.86% to 2.68%, the amount of the Ca2Mg6Zn3 phase gradually decreases but that of the I (Mg3YZn6) and W (Mg3Y2Zn3) phases gradually increases. Furthermore, an increase in Y content from 0.86% to 2.68% also causes the grain size of the as-cast alloys to gradually decrease. In addition, the tensile and creep properties of the as-cast alloys vary with Y content. Namely, with Y content increasing from 0.86% to 2.68%, the creep properties gradually increase, whereas the tensile properties firstly increase and attain the maximum at 1.77% Y, beyond that they decrease. Amongst the as-cast alloys with 0.86% Y, 1.19% Y, 1.77% Y and 2.68% Y, the alloy with 1.77% Y exhibits the relatively optimal tensile and creep properties.