Effects of Alloying Elements on Elastic, Stacking Fault and Diffusion Properties of Fcc Ni from First-principles: Implications for Tailoring the Creep Rate of Ni-base Superalloys

Abstract

To understand the effects of alloying elements on the creep rate of Ni-base superalloys, factors entering into a secondary creep rate are calculated via first-principles calculations based on density functional theory for 26 Ni 31 X systems where X = Al, Co, Cr, Cu, Fe, Hf, Ir, Mn, Mo, Nb, Os, Pd, Pt, Re, Rh, Ru, Sc, Si, Ta, Tc, Ti, V, W, Y, Zr, and Zn. They are volume, elastic properties, stacking fault energy, and diffusivity. It is found that shear modulus, Young's modulus, and roughly stacking fault energy show inverse correlation to the atomic volume of the system. In addition, the closer the alloying elements to Ni, with respect to atomic volume and atomic number, the larger the predicted shear modulus, Young's modulus, and stacking fault energy. Diffusivity calculations show that mid-row 5d transition metal elements, particularly Re, Os, and Ir, have the highest activation barrier for diffusion, while far-right or far-left row placement elements such as Y, Zn, and Hf, have the lowest activation energy barriers for diffusion. A creep rate ratio of ߝሶ ே యభ ߝሶ ே ⁄ is calculated and the effect of the alloying elements shows 13 systems have a decreased creep rate relative to Ni, while 13 systems have an increased creep rate relative to Ni.