Ordered domain interfaces formed between DO22 (Ni3V) phases along [100] direction during the precipitation process of Ni75AlxV25-x alloys were simulated by using the microscopic phase-field model. The atomic structure, migration process, and compositions of interfaces were investigated. It is found that there are four kinds of stable ordered domain interfaces formed between DO22 phases along [100] direction and all of them can migrate. During the migration of interfaces, the jump of atoms shows site selectivity behaviors and each stable interface forms a distinctive transition interface. The atom jump selects the optimist way to induce the migration of interface, and the atomic structures of interfaces retain the same before and after the migration. The alloy elements have different preferences of segregation or depletion at different interfaces. At all the four kinds of interfaces, Ni and Al segregate but V depletes. The degrees of segregation and depletion are also different at different interfaces.
On the basis of the microscopic phase-field dynamic model and the microelasticity theory, the characteristics of the coarsening behavior of γ′ phase in Ni-Al alloys have been systematically studied in a certain volume fraction of the precipitates. It was found that the initial irregular shape, randomly distributed γ′ phase, gradually transformed into cuboidal shape, regularly aligned along the [100] and [010] directions, and a highly preferential selected microstructure was formed during the later stage of precipita-tion. The volume fraction of the precipitates produced some effects on the precipitate morphology but did not produce an obvious ef-fect on the regularities of precipitate distribution. The coarsening rate constant from the cubic growth law decreased as a function of volume fraction for small volume fractions, remained constant for intermediate volume fractions, and increased as a function of volume fraction for large volume fractions. During the coherent coarsening process, four "splitting" patterns between γ′ phases, which belonged to different antiphase domains, were produced via particle aggregation, such as an L-shaped pattern, a doublet, a triplet, and a quartet.
