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 Mg-5(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 degrees C for 16 h, the uniform LPSO phases, which are transformed from Mg-5(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 Mg-5(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. (C) 2013 Elsevier B.V. All rights reserved.