The role of antiphase boundaries in the kinetic process of the L12 → D022 structural change of an Ni3Al0.45V0.50 alloy

The influence of antiphase boundaries (APBs) on the kinetic process of the L12 → D022 structural change in an Ni3Al0.45V0.50 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.