Effects of transition elements on the site preference, elastic properties and phase stability of L1₂ γ′-Co₃(Al, W) from first-principles calculations

We performed a systematic study of alloying effects on the site preference, elastic properties and phase stability of L1₂ γ′-Co₃(Al, W) in terms of the first-principles calculations. Up to twenty-one transition metal elements (Sc, Ti, V, Cr, Mn, Fe, Ni, Y, Zr, Nb, Mo, Tc, Ru. Rh, Pd, Hf, Ta, Re, Os, Ir and Pt) were considered in this work. We find that Sc, Ti, V, Cr, Mn, Y, Zr, Nb, Mo, Tc, Hf, Ta, Re and Os favor to occupy the Al site, and Fe, Ni, Ru. Rh, Pd, Ir and Pt favor to occupy the Co site, except for Y, Fe and Ru, other transition metal elements can stabilize the L1₂ γ′-Co₃(Al, W) at 0 K. By using stress-strain method, the elastic properties including bulk modulus, shear modulus and Young's modulus were evaluated. It is verified that the elastic properties of L1₂ γ′-Co₃(Al, W) depend on not only volume change but also electron density as well as electronic configurations. The thermodynamic results of phase stability of L1₂ γ′-Co₃(Al, W) reveal that Hf, Ti and Ta are the promising alloying elements to improve the stability of L1₂ γ′-Co₃(Al, W).