近全层组织γ-TiAl基合金的室温拉伸断裂机理

通过对直缺口近全层组织的扫描电镜原位拉伸实验以及相应的断裂表面观察，结合有限元计算了TiAl基合金近全层组织拉伸的断裂机理。研究表明：许多裂纹在塑性变形前沿着层间起裂和扩展，断裂过程的驱动力是拉应力。在直缺口试样中，许多裂纹直接起裂于缺口根部，并且沿着层间扩展。随着拉应力的增加，主裂纹和新裂纹也可以通过障碍晶粒的穿层解理断裂来连接。通过有限元计算得沿层断裂强度大约为50MPa，穿层断裂强度大约为120MPa。

Study on Tensile Fracture Mechanisms of γ-TiAl Alloys for Near Fully-Lamellar Microstructure at Room Temperature

In situobservations of fracture processes, combined with one to one related observations of fracture surfaces and finite element method (FEM) calculations, are carried out on notched tensile specimens of TiAl alloys for near fully-lamellar microstructure. The results reveal that most cracks are initiated and propagated at the interfaces between lamellae before plastic deformation. The driving force for fracture process is the tensile stress. In specimens with a slit notch, most cracks are initiated directly from the notch root and extend along lamellar interfaces. The main crack and a new crack are then linked by the translamellar cleavage fracture of the barrier grain with the increasing applied load. FEM calculations reveal that the strength along lamellar interfaces (interlamellar fracture) is as low as 50 MPa , appreciably lower than the strength perpendicular to the lamellae (translamellar fracture), which shows a value higher than 120 MPa.