Alloying-element dependence of structural, elastic and electronic properties of nickel-based superalloys: Influence of γ’ volume fraction

Abstract

Abstract First-principles calculations are carried out to investigate the structural, elastic, and electronic properties of nickel-based model superalloys. The effects of alloying element X (where X = Hf, Ta, Mo, W, Cr, Re, Ru, or Co) on the mechanical characteristics of Ni/Ni3Al ternary multilayer structures are obtained and discussed. The γ ’ -volume-fraction dependence of mechanical performance is studied in detail for the first time and the calculated elastic parameters are in good agreement with experimental results at room temperature. The influence of alloying elements on bulk modulus is almost independent of γ ’ volume fraction. While the effects of alloying elements on shear modulus, Young’s modulus, the ductile and brittle behavior, some particular orientation-dependent elastic moduli and Zener anisotropy factor are closely related to γ ’ volume fraction. Alloying additions increase the Young’s and shear moduli, reduce the ductility and lower the anisotropy performance, but the degree of influence on these properties varies with γ ’ volume fraction. Among the three γ ’ volume fractions investigated in this work, nickel-based ternary model superalloys with 60% γ ’ volume fraction have significant improvement in Young’s and shear moduli and thus possess the best comprehensive elastic performance. Furthermore, covalent-like bonding between alloying dopants and host atoms and strong X d- Ni d hybridization account for the superior elastic properties of superalloys with alloying additions. Alloying dopants and Ni atoms from the interface and two phases share a DOS peak just below the Fermi level, and this additional d-d hybridization leads to the exceptional mechanical performance of superalloys with 60% γ’ volume fraction.