First-principles study on the elastic anisotropy and thermal properties of Mg–Y compounds

Abstract

Magnesium (Mg) alloys are widely used in automobile, rail transit, and other fields; however their heat resistance and deformation ability should be improved. In the present work, the structural characteristics, dynamic stability, mechanical anisotropic, electronic structure, and thermal properties of Mg-Yttrium (Y) binary compounds are systematically explored using the first-principles calculations combined with the quasi-harmonic approximation. The current calculated first-principles results reveal that MgY, Mg2Y, and Mg24Y5 are confirmed the dynamically and thermodynamically stable phases at 0 K by the phonon dispersions with no imaginary frequency and formation enthalpy convex hull graph. The calculated mechanical properties of Mg–Y compounds are gradually increased with the increase of Y content, and MgY has the largest elastic moduli, including bulk, shear, and Young's modulus, as the values with 43.82, 26.7, and 66.63 GPa, respectively. The elastic anisotropies of the Mg–Y system are illustrated by elastic anisotropy indexes and three-dimensional surface constructions, and these results show that the sequence of elastic anisotropy are MgY > Mg2Y > Mg24Y5. Additionally, the MgY phase exhibits superior heat resistance compared to the Mg2Y and Mg24Y5 phases, which is beneficial to enhance the heat resistance of Mg alloys.