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 L1(2) -> D0(22) 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 L1(2) structure and V diffusion in the L1(2) 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 D0(22) regions, because the combination of the migrated APBs produced the APSPs in the L1(2) structure. On this basis, it is proposed that the APBs bring together the two kinetic factors in the process of the L1(2) -> D0(22) structural change, the physical origin of which is the variation in the charge density distribution of the APDs due to APB migration. (c) 2006 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.