Effect of Addition of Nd and Ca on Microstructure and Mechanical Properties of As-cast Mg-Gd-Zr Alloy
Mg-6Gd-0.5Zr alloy(GK60),Mg-4Gd-2Nd-0.5Zr alloy(GNK420)and Mg-4Gd-1Nd-1Ca-0.5Zr alloy(GNXK4110)were prepared by the metal mould casting method.The effects of Nd replacing Gd element and simultaneous substitution of Nd and Ca elements for Gd elements in Mg-6Gd-0.5Zr alloy on the microstructure and mechanical properties of the alloy were investigated.The results reveal that the grain size of the alloy decreased significantly with the variety of alloy elements when the total amount of elements is constant.The average grain size decreased from 114.59 μm in GK60 alloy to 102.69 μm in GNK420 alloy and 79.51 μm in GNXK4110.The second phase evolved from Mg5Gd and Mg3Gd to Mg5(Gd,Nd)and then to Mg7(Gd,Nd,Ca).Meanwhile,the number of the second phase increased significantly.The yield strength(YS)and ultimate tensile strength(UTS)of the three alloys increase gradually due to grain refinement and second phase strengthening,while the elongation(EL)first decreases and then increases.The GNXK4110 alloy obtained the best mechanical properties,the YS and UTS reached 98.36 MPa and 162.5 MPa,respectively,and the EL reached 7.97%.