Abstract:Microscopic phase-field model was used to study the effect of atomic structure of interfaces and phase transformation direction on the composition evolution of heterointerfaces (including ordered domain interfaces formed between L1₂ and DO₂₂ phases and order-disordered interfaces) in Ni₇₅Al_xV_25-x alloys. The results demonstrate that V depletes at the DO₂₂ side and segregates at the L1₂ side, and Al segregates at the DO₂₂ side and depletes at the L1₂ side of ordered domain interfaces formed between L1₂ and DO₂₂ phases during the phase transformation L1₂ DO₂₂. The composition of Ni at the ordered domain interfaces is affected by the phase transformation and atomic structure of interfaces. During the phase transformation L1₂→DO₂₂, Ni segregates at the interfaces which can migrate during the phase transformation. While at the interfaces (002)_D//(001)_L, Ni segregates at the L1₂ side and depletes at the DO₂₂ side, which is the same as the ordered domain interfaces formed between L1₂ and DO₂₂ phases during the phase transformation DO₂₂→L1₂. At the interface formed between DO₂₂ and disordered phase, Ni and Al segregate and V depletes. However, at the interface formed between L1₂ and disordered phase, Ni and Al deplete and V segregates. The tendency of segregation or depletion of alloy elements is unchanged with the ordered domain interface because of the solute drag effect, but the degree of segregation or depletion of alloy elements is changed.

Key words: Ni₇₅Al_xV_25?x alloys; microscopic phase-field; ordered domain interface; order-disordered interface; solute segregation