Effects of N, O, S on generalized stacking fault energies and dislocation movements in γ-Ni and γ′-Ni3Al

The effects of interstitial atoms (N, O and S) on generalized stacking fault energies in the gamma-Ni and gamma '-Ni3Al were systematically elucidated by first-principles calculations. N, O and S atoms had the preference for octahedral interstitial sites in gamma phase. N and S atoms had the preference for octahedral interstitial site with 6Ni atoms in gamma ' phase, while O atom had the preference for octahedral interstitial site with 2Al4Ni atoms. With the addition of adopted atoms, the intrinsic stacking fault energy in gamma phase was decreased and the anti-phase boundary energy in gamma ' phase was increased, which were attributed to the charge redistribution between the adopted atoms and neighbouring Ni atoms. The addition of N, S, especially O, hindered the extended dislocation movement and enhanced its formation probability. The addition of O and S atoms significantly enhanced the formation probability of Kear-Wilsdorf dislocation lock in gamma ' phase, while the addition of N slightly reduced it.