Crystallographic Insights Into the Onset of Internal Fatigue Fracture in a Beta Titanium Alloy via multiscale SR‐CT and EBSD

This study investigated the crystallographic features of internal fatigue crack initiation sites in beta Ti alloys using a combination of synchrotron radiation computed tomography and focused ion beam/electron backscatter diffraction analyses. Adjoining facets were observed at the crack initiation site; however, their formation occurred in sequence and was related independently to the crack initiation and propagation. Moreover, the adjoining facets may correspond to distinct microstructures. The first facet was observed between two beta grains and was associated with a continuous layer of the alpha phase along the grain boundary. Conversely, the facet formed by the crack propagation process was related to a transgranular fracture process within a beta grain. The debonding‐like behavior between the alpha and beta phases is a potential mechanism responsible for the initiation of internal cracks.