Exploring alloying effect on phase stability and mechanical properties ofγ″-Ni3Nb precipitates with first-principles calculations

Abstract

The superior mechanical strength of Inconel 718 and similar Nb containing alloys mainly results from the ordered γ″-Ni3Nb precipitates. By employing first-principles calculations, we comprehensively investigate the effects of alloying elements (i.e., Sc, Ti, V, Cr, Mn, Fe, Co, Y, Zr, Mo, Tc, Ru, Rh, Pd, Hf, Ta, W, Re, Os, Ir, and Pt) on site preference, phase stability and mechanical properties of the γ″-Ni3Nb. The calculation results indicate that Sc, Ti, V, Y, Zr, Mo, Hf, Ta and W prefer to occupy the Nb sublattice, and others tend to occupy the Ni sublattice. Nb-sublattice and strong Ni-sublattice occupying elements can thermodynamically stabilize the γ″-Ni3Nb. Meanwhile, the introduction of W, Os, Ta or Mo is beneficial to the enhancement of the elastic moduli of the γ″-Ni3Nb. All studied phases present inherent ductile and strong elastic anisotropic. The alloying elements, except for Pd, Hf, Zr and Mn, will cause the increase of the Vickers hardness of the γ″-Ni3Nb. Furthermore, the electronic structures are analyzed to trace the influence mechanism of alloying elements on the stability and mechanical properties. This work provides insights into the improvement of stability and mechanical properties of Inconel 718 and the design of the γ″-strengthened novel alloys.

Keywords

• Inconel 718 superalloy
• γ″-Ni3Nb phase
• First-principles calculations
• Site preference
• Mechanical properties
• Electronic structure