Microscopic phase-field study on order-disorder transition of the antiphase domain boundary formed between L1₂ phases

Kinetics of order-disorder transition at antiphase domain boundary (APDB) formed between L1₂ (Ni₃Al) phases is investigated using microscopic phase-field model. The results demonstrate that whether order-disorder transition happens or not depends on the atomic structure of the APDB. Accompanied with the enrichment of V and depletion of Ni and Al, the ordered APDB with phase-shift vector of a/2[100] transforms into a thin disordered phase layer. Whereas at the APDB with phase shift vector of a/2[110], which remains ordered with temporal evolution, Ni and Al enrich and V depletes. Composition evolution of APDB with order-disorder transition favors the nucleation of DO₂₂ phase, and the formation of disordered phase layer accelerates the growth of DO₂₂ phase. The disordered phase caused by order-disordered transition of the APDB can be considered as the transient phase along the precipitation path of DO₂₂ phase.