First-principles investigation of alloying effects on stacking fault energies and lattice constants of γ′′-Ni3Nb: A comprehensive study

The impact of solute elements on the stacking fault energies (SFE) in γ′′-Ni₃Nb is imperative to ascertain to design of new Ni-based superalloys. Although few experimental studies are available that determine the SFE in Ni alloys, a comprehensive and systematic study on the effect of solute elements on γ′′-Ni₃Nb is unknown. In this study, first-principles calculations based on density functional theory were employed to investigate the effect of solutes. All the relevant d-block elements were evaluated. Substitutions at Ni and Nb sites were examined to assess their effects on intrinsic stacking fault (ISF), superlattice intrinsic stacking fault (SISF), and anti-phase boundary (APB-I) energies. The study elucidated that Ti, V, Co, and Fe are expected to inhibit the formation of detrimental delta phase and improve the mechanical properties. These findings offer insights into optimizing γ′′-strengthened Ni-based superalloys through tailored alloying strategies for enhancing the application of these alloys.