Theoretical investigation of interstitial atoms on generalized stacking fault energy and critical resolved shear stress of Ni

In order to clarify the influence of interstitial atoms on the strength of Ni, the effects of interstitial atoms C, H and O on the generalized stacking fault energy (GSFE) of Ni are investigated by First-principles methods. With the GSFEs as input values, the critical resolved shear stress (CRSS) is calculated. The results reveal that compared to H and O, C can significantly reduce the intrinsic stacking energy (γ_isf) of Ni which implies it can obviously enhance the creep strength of Ni. The effect sequence of interstitial atoms on the CRSS is: Ni–O > Ni–C > Ni–H > Ni, which means O atom has the most significant enhancement effect on plasticity. The charge density differences (CDD) analysis show that the electron distribution around the C atom is more obviously directional, which means a relatively strong covalent bond is formed between the C atom and Ni atom. Furthermore, the d orbital of C appears a much deeper pseudogap near the Fermi energy level. It is consistent with the results of CCD analysis, indicating that the relatively strong bonds between atoms C and Ni lead to a significant reduction in the free energy of Ni–C system, which in turn reduces the γ_isf of Ni.