Enhanced tensile strength of TiAl/Ti₂AlNb diffusion bonding joint by a novel post-bonded hot deformation

Dissimilar TiAl-based alloys weld by solid-state bonding, also known as diffusion bonding (DB), usually show brittle intermetallic compounds, high interfacial stress, and poor properties. A novel post-bonded process strategy, slight deformation in the direction of stress parallel to the bonding interface, was developed in the post-bonded treatment of the TiAl/Ti₂AlNb joint. The effect of post-bonded processes on the interfacial microstructure, element diffusion, fracture characteristics and mechanical properties were systematically investigated. The results showed that the post-bonded hot deformation (PBHD), compared to the traditional post-bonded heat treatment (PBHT), can effectively increase the major elements diffuse and the growth of the reaction layer, as well as promote the precipitates which distribute uniformly in the reaction layer, finally resulting in superior tensile strength. Compared with the DB samples, the ultimate tensile strength of the PBHD joint increased by 45.58%. In addition, the fracture behavior was further analyzed based on the microfracture morphology and crack propagation path. These findings will facilitate the development of advanced manufacturing processes of blisk for high-temperature light alloys.