Site occupation evolution of alloying elements in L12 phase during phase transformation in Ni75Al7.5V17.5

Abstract Based on the microscopic phase-field model, the correlation between site occupation evolution of alloying elements in Ni 3 V-DO 22 phase and growth of Ni 3 Al-L1 2 phase was studied during the phase transformation of Ni 75 Al 4.2 V 20.8 . 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 DO 22 phase almost remains unchanged; at the late stage, the compositions of Ni and Al decrease while V increases in DO 22 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 DO 22 phase. Ni is mainly supplied from V sublattice, and part of Al is supplied from Ni i and V sites at the centre of DO 22 phase. The excessive V from the decreasing DO 22 phase migrates into the centre of DO 22 phase and mainly occupies V and Ni II sites. It is the site occupation evolution of antisite atoms and ternary additions in DO 22 phase that controls the growth rate of L1 2 phase at the late stage.