First-principles Study on the Elastic Anisotropy and Thermal Properties of Mg–Y Compounds

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 sta-bility, 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 approxi-mation. 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.