Effect of Cooling Path on Precipitation Behavior, Microstructure, and Texture Evolution of Micro-alloyed Magnesium Alloy

Abstract

Alloying with rare-earth (RE) elements enhances the formability of magnesium (Mg) alloys, especially for the lower elevated temperatures. The beneficial effect brought by RE addition is related to texture modification. However, the complexity of the precipitation behavior in RE-containing alloy and the often excessive RE additions has impeded the understanding of the mechanism for RE texture modification. The current study is based on three micro-alloyed Mg-1Zn-xNd (wt.%) alloys with reduced levels of Nd, i.e., x = 0.1, 0.2, and 0.5 wt.%. Two different cooling paths were employed after solutionizing to achieve different precipitation conditions. The alloys were then subjected to hot rolling at 450 °C to a total reduction of 45% in two passes, and post-deformation annealing was also conducted. The precipitation behavior of the current alloy was discussed based on experimental observations and thermodynamic simulations. It was found that “dilute” Nd in solid solution is more effective in suppressing both dynamic and static recrystallization compared to Nd in the form of precipitates. Ultimately, a non-basal texture with basal poles splitting toward rolling direction and transverse direction was obtained for the Mg-1Zn-0.5Nd alloy after annealing. The mechanism of texture weakening effect was attributed to the presence of Nd in solid solution.