Mechanical and thermal conductivity properties of enhanced phases in Mg-Zn-Zr system from first principles

In this paper, the mechanical properties and minimum thermal conductivity of ZnZr, Zn₂Zr, Zn₂Zr₃, and MgZn₂ are calculated from first principles. The results show that the considered Zn-Zr intermetallic compounds are effective strengthening phases compared to MgZn₂ based on the calculated elastic constants and polycrystalline bulk modulus B, shear modulus G, and Young's modulus E. Meanwhile, the strong Zn-Zr ionic bondings in ZnZr, Zn₂Zr, and Zn₂Zr₃ alloys lead to the characteristics of a higher modulus but lower ductility than the MgZn₂ alloy. The minimum thermal conductivity of ZnZr, Zn₂Zr, Zn₂Zr₃, and MgZn₂ is 0.48, 0.67, 0.68, and 0.49Wm^-1 K^-1, respectively, indicating that the thermal conductivity of the Mg-Zn-Zr alloy could be improved as the precipitation of Zn atoms from the α-Mg matrix to form the considered Zn-Zr binary alloys. Based on the analysis of the directional dependence of the minimum thermal conductivity, the minimum thermal conductivity in the direction of [110] can be identified as a crucial short limit for the considered Zn-Zr intermetallic compounds in Mg-Zn-Zr alloys.