Cast microstructures and mechanical properties of Mg-Nd-Gd-Zn-Zr magnesium alloys

With the method of orthogonal experiment, nine kinds of Mg-Nd-Gd-Zn-Zr magnesium alloys with different composition were prepared by sand casting. The cast microstructures and mechanical properties of Mg-Nd-Gd-Zn-Zr magnesium alloys were investigated, and the effects of Gd and Nd element on mechanical properties at room temperature were also studied by analyzing experiment results of mechanical properties. It is found that the as-cast microstructure of Mg-Nd-Gd-Zn-Zr alloys consists of α-Mg grains with Mg12Nd phase in the grain boundary. After the solid solution treatment, almost all of the phases in the grain boundary dissolved in the matrix; however, there was still discontinued Mg12Nd phase in the boundary. The increasing Gd content results in higher ultimate strength, yield strength and elongation. With increasing Nd content, the ultimate strength, the yield strength and the elongation increase. However, the elongation decreases when Nd is over 2.85 wt%. The effects of Nd content on the ultimate strength and yield strength of Mg-Nd-Gd-Zn-Zr alloy at room temperature are more significant than that of Gd. When Zn content is increased, the yield strength increases, but the ultimate strength and the elongation decreases. And Zn content has the greatest impact on elongation.