Generalized stacking fault energies, ductilities, and twinnabilities of Ni and selected Ni alloys

The generalized stacking fault energies, Rice-criterion ductilities, and twinnabilities of selected Ni-$x$ solid-solution alloys ($x=\mathrm{Nb}$ , W, Mn, Fe, Cu) are calculated using density functional theory to elucidate how alloying alters the mechanical properties of pure Ni. Relative to Ni, the alloys have smaller stacking fault energies $\left({\gamma }_{\mathrm{sf}}\right)$ , similar ductilities, and a greater tendency to undergo deformation twinning. The results are compared to experimental studies of the mechanical properties of nanocrystalline (nc) Ni alloys from the literature, and it is suggested that the higher strain-hardening rate recently reported for nc-Ni-Cu (relative to nc-Ni-Fe) does not arise from differences in ${\gamma }_{\mathrm{sf}}$ , but from a higher dislocation density caused by more facile dislocation nucleation.