Effect of Nd on the microstructure and mechanical properties of Mg-8Gd-5Y-2Zn-0.5Zr alloy

Microstructures and mechanical properties of the Mg-8Gd-5Y-2Zn-0.5Zr-xNd (x=0, 0.5, 1 and 2 wt%) alloys in the as-cast, solid solution and as-aged conditions have been investigated. The experimental results reveal that Nd can impede the formation of LPSO phases during the solidification process and suppress the transformation of Mg5(Gd, Y, Zn) to LPSO phase at high temperature heat-treatment. Addition of 2% Nd leads to the disappearance of the LPSO phases in the as-cast alloy. After heat-treatment at 520 °C for 16 h, the uniform LPSO phases, which are transformed from Mg5(Gd, Y, Zn) phases and refined by the Nd, result in a higher solid solubility and greater aging effect. With increasing Nd content, the residual Nd-rich Mg5(Gd, Y, Zn) phases in the solid solution alloys gradually increase and produce an adverse effect on the mechanical properties. The alloy with the addition of 0.5% Nd shows the optimal mechanical properties in the as-aged alloys, and its ultimate tensile strength, yield strength and elongation are 308 MPa, 252 MPa and 5.3%, respectively.