Abstract:Based on the microscopic phase-field model, the correlation between site occupation evolution of alloying elements in Ni₃V-DO₂₂ phase and growth of Ni₃Al-L1₂ phase was studied during the phase transformation of Ni₇₅Al_4.2V_20.8. The results demonstrate that the growth of L1₂ 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 L1₂ 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_Ⅰ 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 L1₂ phase at the late stage.

Key words: Ni₇₅Al_4.2V_20.8 alloy; grain growth; phase transformation; microscopic phase-field; antisite defect