带缺口的熔模铸造TiAl合金断裂特性的扫描电镜原位观察(英文)

采用感应凝壳熔炼技术和熔模铸造方法制备TiAl合金。在增量加载情况下,采用扫描电镜原位观察技术观察带缺口的熔模铸造TiAl合金试样的裂纹扩展和断裂特性。在拉伸变形的整个过程中,观察并分析裂纹萌生、扩展直至断裂的全过程。结果表明,TiAl合金的断裂机制不仅对于缺口区域附近的微裂纹敏感,而且与层片方向和加载轴的位向有关。当局部应力大于TiAl合金的断裂韧性时,高的拉伸应力就会导致裂纹萌生、扩展直至断裂失效。因此,TiAl合金的塑性和高的拉伸应力导致带缺口的TiAl合金的断裂失效。

Fracture characteristics of notched investment cast TiAl alloy through in situ SEM observation

TiAl alloys were produced by investment casting method combined with induction skull melting （ISM） technique. In situ scanning electron microscopy （SEM） was utilized to study the fracture characteristics and crack propagation of a notched investment cast TiAl specimens in tension under incremental loading conditions. The whole process of crack initiation, propagation and failure during tensile deformation was observed and characterized. The results show that the fracture mechanism was sensitive to not only the microcracks near the notched area but also lamellar orientation to loading axis. The high tensile stress leads to the new microcracks nucleate along lamellar interfaces of grains with favorable orientation when local stress intensity reaches the toughness threshold of the material. Thus, both plasticity and high tensile stress are required to cause notched TiAl failure.