Segregation behavior of alloying elements and its effects on stacking fault of γ′ phase in Ni-based superalloys: First-principles study

In this paper, the segregation tendency of elements M (Re, Co, Cr, Mo, Ti) near the complex and intrinsic stacking fault (CSF and SISF) on γ′- Ni₃Al (111) plane as well as the influence of the segregation on the mechanical properties were studied by the first-principle method. The results show that Co and Cr atoms tend to segregate to CSF and Co also has segregation tendency for SISF. Comparison of metallic radius of alloying element can predict preliminary the segregation tendency which decreases along with the increase of metallic radius of M, except for Re. Segregation of M depends on their strong interactions with their surrounding Ni atoms near SFs, rather than the minimization of elastic strain. In addition, the Re effect is not induced by its interaction with the two SFs in γ′ phase. Meanwhile, the effects of segregated elements Co and Cr on the mechanical properties are further discussed. The results show that segregation of the two elements to CSF results in higher interfacial stability and the improvement of plastic deformation ability, but Co near SISF is beneficial to increase work-hardening. This work will provide insight for the composition design and improvement of processing technology of Ni-based superalloys and even other alloys.