Accelerating exploitation of Co-Al-based superalloys from theoretical study

The discovery of γ′-Co₃(Al,W) opens up a pathway to exploit novel Co-Al-based alloys as candidates of the next generation of superalloys. Inspired by the unexpected finding of γ′-Co₃(Al,W), we present a comprehensive investigation concerning the effect of alloying elements on phase stabilities and mechanical properties of Co₃Al. Up to 22 transition metal elements, e.g. Sc, Ti, V, Cr, Mn, Fe, Ni, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Hf, Ta, W, Re, Os, Ir, and Pt, are considered. Results show that W, Ti, Re, V, and Ta favor to occupy the Al-sublattice. Pd, Pt, Rh, Ni, Ir, Fe, and Ru favor to occupy the Co-sublattice. The others can occupy both the Co- and Al-sublattices. W, Ta, V, Ti, Nb, Re, Mo, Pt, and Cr are shown to stabilize Co₃Al. It verifies that elastic properties are roughly in inverse proportional to the volume change induced by alloying elements within each group of 3d, 4d, or 5d. Based on the analysis of electronic configurations, the influence mechanism of alloying elements is traceable from the chemical bonding and the geometry of charge density. The present calculations are in favorable accord with available experimental data in the literature.