Fracture toughness anisotropy of Ti17 disk fabricated by through-transus-processed forging and the role of toughening mechanisms

The fracture toughness anisotropy of the Ti17 disk fabricated by through-transus-processed forging was discussed. For the specimens in different directions, the fracture initiation toughness K_i was calculated through the crack tip opening displacement, and the contribution of the crack tip blunting and dimple formation to the fracture initiation toughness was distinguished. Furthermore, the origin resulting in the fracture toughness anisotropy was analyzed according to the energy criterion for fracture. The results reveal that the specimen directions have a significant influence on the global fracture toughness and the crack propagation path. Meanwhile, the fracture initiation toughness occupies a significant portion of the global fracture toughness, and it reflects the ability of the crack tip plasticity. In addition, a schematic illustration is applied to demonstrate the toughening mechanism. This reveals that the different specimen directions result in the crack deflection or shearing off the ligament, leading to increased fracture toughness compared with the weak specimen direction.