单晶γ-TiAl合金疲劳裂纹扩展机制的原子模拟

Atomic Simulation of Fatigue Crack Growth Mechanism of Single Crystal γ-TiAl Alloy

为了研究TiAl合金的疲劳性能、裂纹扩展与组织形态的关系,采用分子动力学方法和速度加载的方式,对含内嵌边界裂纹的单晶γ-TiAl合金在交变载荷循环加载下,微裂纹扩展及微观形变机制进行研究。结果表明:单晶γ-TiAl合金在交变载荷的循环加载下裂纹扩展过程及微观形变机制分为三个阶段,其力学性能受加载过程中出现的裂纹尖端晶格畸变,棱柱位错滑移,Lomer-cottrell位错群形成,堆垛层错开动,形变孪晶等各种微观缺陷及其相互作用结果影响,不同阶段的裂纹扩展机理及塑性形变机制完全不同。

In order to study the relationship of fatigue property 、crack growth and organization form of TiAl alloy,the micro crack growth and micro deformation mechanism of single crystal γ-TiAl alloy with an embedded boundary crack under cyclic loading were studied by means of molecular dynamics and velocity loading. Results show that the crack growth process and micro deformation mechanism of single crystal γ-TiAl alloy under cyclic loading were divided into three stages. The mechanical properties are affected by the defects of crack tip lattice distortion,prismatic dislocation slip,Lomer-cottrell dislocation group formation,stacking fault start,deformation twin,etc. and their interaction results in the loading process. The mechanism of crack growth and the mechanism of plastic deformation at different stages were quite different. The research results provide a strong theoretical guidance for improving the performance of γ-TiAlalloys under complex external loading conditions.