Ni75Al_xV_(25-x)合金中异相界面成分演化的微观相场模拟

Microscopic phase-field simulation of composition evolution of heterointerfaces in Ni75Al_xV(25-x) alloys

采用微观相场模型研究界面原子结构和相变方向对Ni75AlxV25-x合金中异相间有序畴界和有序/无序相界成分演化的影响。结果表明:在异相间有序畴界处,V在有序畴界的DO22相一侧贫化,在有序畴界的L12相一侧偏聚;Al则在有序畴界的DO22相一侧偏聚,在有序畴界的L12相一侧贫化。Ni在异相间可迁移有序畴界处的成分受相变方向和界面结构的影响。在DO22相与无序相之间形成的相界处,Al和Ni偏聚,V则贫化;在L12相与无序相之间形成的相界处,Al和Ni贫化,V则偏聚。由于溶质拖拽效应,合金元素在有序畴界处的偏聚和贫化倾向不随有序畴界迁移改变,但程度变化。

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 A1 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 LI2 and DO22 phases dttring the phase transformation DO22→L12. At the interface formed between DO22 and disordered phase, Ni and A1 segregate and V depletes. However, at the interface formed between L12 and disordered phase, Ni and A1 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.