The effects of solutes on precipitated phase/matrix interface stability and their distribution tendencies between the two phases in Co-based superalloys

Abstract

D019-Co3X and μ-Co7X6 are two common detrimental phases in Co-based superalloys. In this work, the D019-Co3X/γ and μ-Co7X6/γ interfaces were studied by density functional theory (DFT) calculation. On this basis, the influence of different solutes on the interfacial stability has been analyzed. For the D019/γ interface, Ti can lower its stability and reduce the driving force of D019’s nucleation, which is different from other elements. W, Re, and Ru can increase the interfacial stability, promoting the nucleation of D019. For μ/γ, these solutes all increase the work of separation of the interface, but compared with other solutes, Ti can hardly improve the work of separation and facilitate the nucleation of the μ phase. In addition, the solute distribution behaviors between D019 (or μ) and γ have been discussed. It is found that when solutes such as Ti are distributed in D019, the energies are all more stable than they are inside γ, and they all have the tendency to diffuse from γ to D019. For the μ and γ phases, Ti is different from other solutes since its energy to distribute in γ is more stable than that distributed in μ. During the growth of μ, the Ti inside γ has no tendency to diffuse toward μ. These results reveal the solutes’ effects on the precipitation of the D019 and μ phases at the atomic scale from the perspective of interfacial stability and atomic diffusion.