First-principles calculation of the structural, electronic and mechanical properties of β′ phase in Mg-RE binary systems

Abstract

Rare-earth magnesium alloys (Mg-RE) are gaining growing prominence across multiple industries due to their superior mechanical properties and enhanced formability compared to conventional magnesium alloys. β′ phase of Mg-RE alloys exhibits remarkable behavior in strengthening and enhancing corrosion resistance. However, the mechanical behaviors of some β′ phases themselves remain unexplored. Therefore, our objective is to identify the mechanical and thermomechanical properties of β′ phases. Herein, a theoretical study to investigate the structural, electronic, elastic and anisotropic properties of β′–Mg7RE phase from first-principle calculations is described. Besides, the melting temperature and Debye temperature of these intermetallic compounds are also predicted. The calculated results confirm the thermodynamic and mechanical stability of all β′–Mg7RE phases. Additionally, the calculated value of bulk modulus for all β′–Mg7RE phase exhibit similarity, with an approximate value of 38 GPa. The degree of anisotropy in the bulk modulus of the β′–Mg7RE phase is relatively lower compared to the shear and Young’s moduli. Among the β′ phase, β′–Mg7Lu exhibits the most pronounced anisotropy. Furthermore, the highest degree of Young’s and shear moduli anisotropy for all β′ phases are observed in the (001) plane. The value of the electron localization function between Mg and RE atoms ranges from 0.48 to 0.56. In more detail, the density of states (DOS) reveals that hybridization arises from strong interaction between the Mg–p states and RE–d states below the Fermi level. Indeed, the results will offer valuable insights into the influential factors on the mechanical properties of the β′ phase, contributing to a more comprehensive understanding of its performance and potential applications.