Microscopic phase-field simulation of composition evolution of heterointerfaces in Ni75AlxV25-x alloys

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 Ni75AlxV25-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.