First-principles investigation of phase stability and elastic properties of Laves phase TaCr₂ by ruthenium alloying

Abstract

Based on the first-principles method of density functional theory, the microscopic mechanism of the effect of addition of alloying element Ru content on the stability and elastic properties of Laves phase TaCr2 was investigated by parameters such as formation enthalpy, electronic structure, and elastic constants. The addition of Ru atoms tends to preferentially occupy the lattice sites of Cr. With the increase in the Ru content, the alloying ability of Ta8Cr16−n Ru n (n = 0–6) becomes progressively weaker, the stability gradually decreases, whereas the Poisson’s ratio grows. The bonding peak appears to drop and widen, weakening the bonding strength of Ta–Cr atoms, rendering the shear deformation to be performed easily, thereby improving toughness. When the Ru content rises to 20.83 at%, the bulk modulus, shear modulus, Young’s modulus, and Poisson’s ratio of the alloy attain the maximum value, the brittleness diminishes to the most extent, the resistance to elastic deformation is the strongest, as well at the optimum fracture toughness.