The effect of the elements Cr, Os, Ir, and Y additions on the mechanical and electronic properties of L12 Ni3Co alloys

This paper studies the site preference and mechanical, thermal, and electronic properties of L12 Ni3Co alloys doped with Cr, Os, Ir, and Y elements based on first-principles calculations. The formation and substitution formation enthalpy results illustrate that the doping elements Cr, Os, and Ir tend to occupy the Ni site and form Ni23MCo8. According to the results of the mechanical properties, we find that except Y, the element doping in the alloys will improve the elastic modulus and hardness, especially Cr. The direction dependence of Young's modulus and acoustic velocities shows that these alloys are all anisotropic in nature but not of great quality. The thermal properties of Debye temperature and minimum thermal conductivity reveal that only Cr doping that forms Ni23CrCo8 can improve thermal conductivity. The electronic structures are analyzed to elucidate the origin of the mechanical properties of alloys, and the results indicate that the strengthening effects of doping elements like Cr are attributed to the enhanced covalent characteristic between Co or Ni and Cr atoms. In summary, it was predicted that Cr, Os, and Ir have a good solid solution strengthening effect in Ni3Co alloys, which is worth further study.