Site occupation evolution of alloying elements in Ni3V phase during phase transformation in Ni75Al4.2V20.8

Based on the microscopic phase-field model, the correlation between site occupation evolution of alloying elements in Ni3V-DO22 phase and growth of Ni3Al-L1(2) phase was studied during the phase transformation of Ni75Al4.2V20.8. The results demonstrate that the growth of L1(2) phase can be divided into two stages: at the early stage, the composition of alloying elements in DO22 phase almost remains unchanged; at the late stage, the compositions of Ni and Al decrease while V increases in DO22 phase. Part of alloying elements for L1(2) phase growth are supplied from the site occupation evolution of alloying elements on three kinds of sublattices in DO22 phase. Ni is mainly supplied from V sublattice, and part of Al is supplied from Ni. and V sites at the centre of DO22 phase. The excessive V from the decreasing DO22 phase migrates into the centre of DO22 phase and mainly occupies V and Ni-II sites. It is the site occupation evolution of antisite atoms and ternary additions in DO22 phase that controls the growth rate of L1(2) phase at the late stage.