Influence of the interface layer on the fracture toughness of Ti2AlNb/Ti6Al4V layered metal composite

Abstract

In this study, the Ti₂AlNb/Ti6Al4V layered metal composite was manufactured through vacuum hot pressing. The fracture toughness (K_IC) of the composite reaches 48.8 MPa∙m^1/2, demonstrating a notable improvement over the Ti₂AlNb alloy. The interface layer formed due to diffusion reactions after hot pressing plays an essential role in enhancing the toughness of the composite. Research indicates that the interface layer is primarily consists of α₂-Ti₃Al phase and β-Ti phase, which have a lower hardness than the two base alloys. The fracture behavior demonstrates that the composite will undergo interface delamination when it expands to the interface layer, which can deflect the main crack and increase the energy release rate, delaying the fracture of the composite. High mechanical stress and soft interfaces are favorable for the occurrence of interface delamination. Simultaneously, the activation of <c+a> dislocations in α₂-Ti₃Al within the interface layer, along with the high accumulation of geometrically necessary dislocations (GND) after fracture, indicates that the interface layer can participate in plastic deformation and coordinate the deformation of the two base alloys. Additionally, the change in material properties from soft to hard during crack propagation reduces the crack driving force and improves fracture resistance.