Thermodynamic Analyzing the Effect of Intermetallic Compounds on Thermal Diffusivity of Mg-La-Zr Alloys

Description

1st Paragraph: Magnesium alloys with rare earth element (RE) exhibited good creep-resistant and high specific strength at elevated temperatures due to the precipitation hardening and the grain boundary strengthening by the intermetallic compounds [1,2]. The phase equilibria of MgLa-Zr were investigated through one diffusion couple of Mg/La_84.6Zr_15.4 and three Mg-LaZr alloys. Figure 1 is the isothermal section of Mg-La-Zr system at 400^oC. Based on experimental data, the thermodynamic description of Mg-La-Zr system was assessed by using CALPHAD method. According to the major effects of solid solubility and second phase distribution on the thermal diffusivity, the selection principle is used to design two alloys with composition of Mg_99.70La_0.18Zr_0.12 and Mg_99.09La_0.78Zr_0.12 were selected. The eutectic microstructure composed of LaMg₁₂ and Mg phases present a dense network (in figure 2.) in Mg_99.09La_0.78Zr_0.12 alloy which may hinder the heat transmission. The Mg_99.70La_0.18Zr_0.12 exhibited good thermal diffusivity.

Authors: WenFei Zhu, Qun Luo, Shuanglin Chen, JieYu Zhang, and Qian Li

Keywords: Thermodynamic Description; Mg-La-Zr Alloys; Thermal Diffusivity