摘要
通过对双态组织的扫描电镜原位拉伸实验、相应的断裂表面观察以及有限元计算,研究了TiAl基合金双态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,断裂发展的驱动力是拉应力.在直缺口试样中,许多裂纹直接起裂于缺口根部,而且起裂于γ晶粒,并沿着层间扩展.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.然而在V型缺口试样中,裂纹则起裂于距缺口根部一定距离处.通过有限元计算得到沿层断裂强度大约为110MPa,穿层断裂强度大约为250MPa,这就是裂纹更容易沿着层间形核及扩展的原因.
By means of in-situ tensile test of the specimen of bi-morphic alloys of γ-TiAl,observation upon its corresponding fracture surface with scanning electron microscope, and finite element computation, the tensile fracture mechanism of these alloys is investigated. The results reveal that most cracks are initiated and propagated along the interfaces between lamellae before the starting of plastic deformation. The driving force of 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 one are then linked by the translamellar cleavage fracture over the barrier grain when the applied load increases. In V-notch specimens, however, a crack may be initiated at a distance in front of the notch root. The FEM calculations reveal that the fracture strength along lamellar interfaces (interlamellar fracture) is as low as 110 MPa and appreciably lower than that along the interfaces perpendicular to the lamellae (translamellar fracture), which shows a value higher than 250 MPa. This explains the reason why cracks nucleate and extend preferably along the lamellar interfaces.
出处
《兰州理工大学学报》
CAS
北大核心
2004年第3期1-6,共6页
Journal of Lanzhou University of Technology
基金
国家自然科学基金(59871015)
关键词
TIAL
拉应力
起裂
断裂
TiAl
tensile stress
crack initiation
fracture
