Lattice stability and the effect of Co and Re on the ideal strength of Ni: First-principles study of uniaxial tensile deformation

摘要

Using first-principles density functional calculations,lattice stability of γ-Ni under [001],[110],and [111] uniaxial tensions and the effect of alloying elements Co and Re on the uniaxial tensile behavior of γ-Ni were studied in this paper.With elastic constants and phonon spectra calculations,we examined the mechanical stability and phonon stability of Ni during the uniaxial tensions along the three characterstic directions.The results show that the mechanical stability and phonon stability of a lattice occurs before the maximum stress-strain point under the [001] and [111] tension,respectively.The effects of Co and Re on the ideal tensile strength of γ-Ni show a significant directivity:Co and Re have little effect on the stresses in [001] and [111] directions,but increases the ideal strength of the system in the weakest uniaxial tensile direction.Moreover,the strengthening effect of Re is significantly better than that of Co.By further analyzing electronic structure,it is found that the effect of alloying elements on the uniaxial tensile behavior of γ-Ni comes from their interactions with host atoms.