全层状TiAl基合金断裂中晶界的双重作用

通过SEM原位拉抻技术和双晶体压缩实验研究了全片层TiAI基合金晶界断裂行为。研究表明，在全层状组织的断裂行为中，晶界具有双重作用。一方面，微裂纹首先萌发于晶界区，其扩展方式取决于晶界两侧片层的取向。另一方面，不同类型的晶界对裂纹扩展的阻力不同，因而对全层状TiAI基合金韧性的作用不同，纵向晶界有助于断裂韧性的提高，而横向晶界对合金韧性不利。

The Twofold Effects of Grain Boundary on Fracture Behaviors in Fully Lamellar TiAl Alloys

Fracture behaviors of grain boundary in fully lamellar TiAl alloys were investigated by in-situ SEM technique and compression of bicrystal. The results indicate that the grain boundaries have twofold effects on fracture behaviors. On one hand, the grain boundaries are the sites of microcrack nucleation, microcracks first occur at grain boundary zone, whose propagation type depends on lamellar orientation of both side of grain boundary. On the other hand, the different grain boundaries have different hindrance effects on propagation of crack, which have corresponding effects on the fracture toughness of FL γ-TiAl alloys. The longitudinal grain boundary is beneficial for enhance for fracture toughness and the transverse grain boundary is bad for the fracture toughness. The dependant relation between fracture toughness and grain size may be elucidated by fracture behavior of grain boundary.