Influence of dilute solute substitutions in Ni on its generalized stacking fault energies and ductility

Abstract

We determine effects of substitutional solutes belonging to 3d, 4d and 5d transition metal (TM) series on volume, intrinsic stacking fault energy (ISFE), unstable stacking fault energy (USFE) and ductility parameter of Ni using first-principles calculations based density functional theory (DFT), considering both ferromagnetic (spin-polarized) and non-magnetic states of Ni. For each of the TM series, we find that volume exhibits a minimum for substitutional elements with half-filled d-orbitals (5 d-electrons). Reduction in ISFE of Ni is seen with all the solute additions except for Pd (in the non-magnetic case). Inclusion of spin-polarization has a pronounced effect on the fault energies and results in increase in both ISFE as well as USFE. In the non-magnetic case, USFE exhibits maxima for alloying with elements having five electrons in d-orbital. Except for Zr and Pd, substitution of other elements enhanced cleavage energy of Ni. Differences in the fault energies on alloying have been explained based on the electronic structure of the alloys. There exists a correlation between change in volume and change in USFE with substitutional alloying. It is envisaged that the exhaustive data generated here would not only form necessary input to multi-scale microstructural modeling, but also help in evolving simple recipes for design of new alloys.