全层状TiAl基合金断裂机理原位观察

In-Situ SEM Study of Fracture Mechanism in Fully Lamellar Ti-49at% Al Alloy

摘要:

通过对裂纹与晶内片层和晶界的交互作用的原位观察，研究了全层状组织TiAl基合金的断裂机制。结果表明：裂纹萌发和扩展方式不仅依赖于片层与拉伸轴的相对取向，还受晶界取向的制约。当片层与拉伸轴成较大角度时，沿片层裂纹扩展是通过主裂纹与沿片层微裂纹的连接及剪切的过程；而当拉伸轴近乎平行片层时，跨片层裂纹依靠对界面分离和跨片层微裂纹这两种形式的微裂纹的连接进行扩展的，纵向交叉晶界有利于断裂韧性的提高，而横向晶界则不利于材料断裂韧性。

Abstract:

The fracture mechanism of fully lamellar Ti 49at% Al alloy has been investigated by studying the interactions between crack and lamellae or grain boundary. The results indicate that the nucleation and propagation mechanism of crack depend on not only lamellar orientation in grain but also the type of grain boundary. As the angle between tensile axis and lamellae is relatively large, main cracks propagate by nucleation, growth and linkage with interfacial microcracks. As the tensile axis is nearly parallel to the lamellae, translamellar cracks propagate by nucleation, growth and linkage with two types of microcracks, e g interface delamination and translamellar microcracks. Different types of grain boundary have different toughening effects on TiAl alloy, that is, interlock grain boundary nearly parallel to the tensile axis is beneficial to fracture toughness, and the grain boundary nearly perpendicular to the tensile axis is not beneficial.