Role of local mode mixity and stress triaxiality in the fracture of niobium/alumina bi-crystal interfaces _ a CPFEM based study

Local mode mixity and stress triaxiality plays an important role during metal/ceramic interface fracture. It has been reported in the literature that the ratio of the fracture energies to the mode I fracture energy can vary from 1 to 5. For many of the bimaterial systems, the reason has been reported to be the local mode mixity and stress triaxiality. Korn et al. [1] performed experimental studies on bicrystal niobium/alumina interfaces and for some orientations the values of the above ratio were reported to be more than 5. However, it was believed that local mode mixity and stress triaxiality might not be the reason for this. In the presented work an effort has been put to explain the role of local mode mixity and stress triaxiality in the fracture of niobium/alumina bi-crystal interfaces using crystal plasticity based constitutive model.