Microscopic phase-field simulation of atomic site occupation in γ′ phases of Ni₇₅Al_25-xFe_x alloy

The microscopic phase-field model based on ternary diffusion form was used to simulating the atomic site occupation and calculating long-range order parameters and concentration etc. in the γ phase of Ni₇₅Al_25-xFe_x alloy. The results show that γ′ precipitation belongs to the mechanism of congruent ordering and spinodal decomposition. With Fe increasing, Fe atomic occupation obviously increases at the β site (the corner site of fcc), Al atoms gradually decrease, and few Ni is found at the β site; on the other hand, Fe atoms have little increase at the α site, Al atoms keep constant, Ni atoms have little decrease. The β site was mostly occupied by Fe and Al atoms, the precipitated γ′ phase is a kind of the Ni₃ (AlFe) single-phase.