Accelerating exploitation of Co-Al-based superalloys from theoretical study. (15th March 2018) - Xu, W.W.
Abstract: 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 Co3 Al. 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 Co3 Al. 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. Highlights: The present study guides the selection of alloying elements for rational design of novel Co-Al-based superalloys. A new energy criterion is proposed to estimate the site preference of alloying elements in Co3 Al. W, Ta, V, Ti, Nb, Re, Mo, Pt, and Cr, especially Ta and Ti, are expected to stabilize Co3 Al. Elastic properties of Co3 Al are inversely proportional to the volume changes induced by alloying elements X. The alloying effect is traceable from electronic hybridizations and topological distributions of charge density. Graphical abstract: Image 2