Microscopic phase-field study on the order-disorder transition of antiphase domain boundary in Ni₇₅Al_xV_25-x alloys

Kinetics of order-disorder transition at antiphase domain boundary (APDB) in Ni₇₅Al_xV_25-x alloys was investigated using microscopic phase-field model. The results demonstrate that accompanied with the enrichment of V and depletion of Ni and Al, the ordered APDBs (200)_L//(200)_L·1/2 [001]_L and (200)_L//(200)_L, which are formed between L1₂ phases, transform into a thin disordered phase layer. Whether order-disorder transition happens or not depends on the atomic structure of the APDB formed between DO₂₂ phases. Accompanied with the depletion of V and enrichment of Ni and Al, order-disorder transition happens at the APDB (001)_D//(002)_D. Whereas at the APDB {100}_D·1/2 [100]_D, which remains ordered with temporal evolution, V is depleted and Ni and Al are enriched. Composition evolution of APDB is order-disorder transition favors the nucleation of the second phase. Some of the grains grow bigger while the others are disappearing during order-disorder transition of APDBs, and the order-disorder transition of APDBs can be considered as the adjoint process of coarsening process of the primary precipitate phase. The kinetics of order-disorder transition at APDB is elucidated at atomic scale, and the function of order-disorder transition at APDB during the microstructure evolution is clarified.