First-principles study on the phase stability of Mg-La and Mg-Nd binary alloys

Abstract

The applications of magnesium alloys in automobile industry are limited by their poor high-temperature creep resistance, which can be effectively improved by rare earth (RE) elements addition. In general, rare earth elements are introduced as mixtures of various kinds of metals, and all of the elements are considered to behave in the same way. In practice, various rare earth elements may act differently in magnesium alloys. La and Nd are the two elements usually added to magnesium alloys. In this paper, first-principles calculations are made to investigate the phase stability of Mg-La and Mg-Nd binary alloy systems. In addition, the solubility of La and Nd in Mg is discussed and the elastic constants of the strengthening phases in Mg-La and Mg-Nd alloys are calculated. The equilibrium phases between Mg 12RE and Mg 3RE are Mg 17La 2 and Mg 41Nd 5 for Mg-La and Mg-Nd systems respectively. The difference of calculated solubility for La and Nd in Mg indicates the distinct strengthening mechanism for these two alloy systems. Mg 3Nd is predicted to have larger elastic moduli and a better strengthening effect than Mg 12La. © right.