The role of antiphase boundaries in the kinetic process of the L1₂ → D0₂₂ structural change of an Ni₃Al_0.45V_0.50 alloy

The influence of antiphase boundaries (APBs) on the kinetic process of the L1₂ → D0₂₂ structural change in an Ni₃Al_0.45V_0.50 alloy has been investigated by transmission electron microscopy. The structural change includes two kinetic factors, i.e., the periodic introduction of antiphase-shifted planes (APSPs) in the L1₂ structure and V diffusion in the L1₂ matrix. Our results revealed that APB migration was accompanied by V diffusion as if to sweep the V atoms out of the antiphase domains (APDs). It was also found that the APBs served as the nucleation sites of the D0₂₂ regions, because the combination of the migrated APBs produced the APSPs in the L1₂ structure. On this basis, it is proposed that the APBs bring together the two kinetic factors in the process of the L1₂ → D0₂₂ structural change, the physical origin of which is the variation in the charge density distribution of the APDs due to APB migration.