The strengthening effects and mechanisms of alloying elements on interfaces for multiphase Ni-based superalloys: A first-principles study

Abstract

The mechanical properties and thermal stability of multiphase Ni-based superalloys are highly determined by the interfaces between the strengthening precipitations and the matrix. In this work, the interface properties of the γ/γ′/γ″ system are investigated using the first-principles calculations, and the strengthening mechanisms of alloying elements (3 d, 4 d and 5 d transition-metals) on the γ/γ″ and γ′/γ″ coexisting interfaces have been evaluated systematically. It was found that the matching configuration of the Ni (Center) + X (termination) is thermodynamically the most stable interface structure. The multi-interfaces doping results demonstrate that W, Re, Mo, Ta, Tc preferably occupy Nb-cp position and Fe, Co, Os tend to substitute Ni-fc position. Among these, W and Re have most significant effect on improving the bonding strength of γ/γ″ and γ′/γ″ interfaces synergistically. The dependence of interfacial cohesion on the metal radius and the concentration of specific elements are discussed as well. The corresponding analysis of electronic structures reveals that the strengthening effect of alloying elements can be ascribed to the increased chemical bonding strength between the doping atom and the nearest-neighbor host atom. The results of this work can shed light on developing novel Ni-based superalloys combinedly strengthened by γ′ and γ″ phases.