Effects of alloying element and temperature on the stacking fault energies of dilute Ni-base superalloys

摘要

A systematic study of stacking fault energy (γSF) resulting from induced alias shear deformation has been performed by means of first-principles calculations for dilute Ni-base superalloys (Ni_(23)X and Ni _(71)X) for various alloying elements (X) as a function of temperature. Twenty-six alloying elements are considered, i.e., Al, Co, Cr, Cu, Fe, Hf, Ir, Mn, Mo, Nb, Os, Pd, Pt, Re, Rh, Ru, Sc, Si, Ta, Tc, Ti, V, W, Y, Zn, and Zr. The temperature dependence of γSF is computed using the proposed quasistatic approach based on a predicted γSF-volume-temperature relationship. Besides γSF, equilibrium volume and the normalized stacking fault energy (ΓSF = γSF/Gb, with G the shear modulus and b the Burgers vector) are also studied as a function of temperature for the 26 alloying elements. The following conclusions are obtained: all alloying elements X studied herein decrease the γSF of fcc Ni, approximately the further the alloying element X is from Ni on the periodic table, the larger the decrease of γSF for the dilute Ni-X alloy, and roughly the γSF of Ni-X decreases with increasing equilibrium volume. In addition, the values of γSF for all Ni-X systems decrease with increasing temperature (except for Ni-Cr at higher Cr content), and the largest decrease is observed for pure Ni. Similar to the case of the shear modulus, the variation of γSF for Ni-X systems due to various alloying elements is traceable from the distribution of (magnetization) charge density: the spherical distribution of charge density around a Ni atom, especially a smaller sphere, results in a lower value of γSF due to the facility of redistribution of charges. Computed stacking fault energies and the related properties are in favorable accord with available experimental and theoretical data.