Microstructure and mechanical properties of vacuum diffusion bonding joints for γ-TiAl based alloy

Vacuum diffusion bonding (DB) of as-extruded Ti-47.5Al-Cr-V (at.%) alloy was carried out at 1000-1100 °C at a pressure of 10-30 MPa for 1-3 h, and the bonded joints were post-bond heat treated (PBHT) at 1360 °C for 0.5 h. Subsequently, the shear strength of all the joints was measured, and the microstructure was observed. The results showed that the shear strength and bonding interface quality of joints increased under as-bonded and PBHT conditions with the increase of each bonding parameter (temperature, pressure, and time). The shear strength of the base material was 486 MPa, and it was 665 MPa after PBHT. Furthermore, the maximum shear strength of the as-bonded joints was over 80% of that of the base material. After PBHT, the maximum strength of the joints was nearly equal to that of the base material. The fracture morphologies of the as-bonded and PBHT joints were analyzed, and the fracture mode was changed from transgranular fracture to intergranular fracture. The optimal bonding parameters were proposed: T ≥ 1050 °C, p ≥ 20 MPa, and t ≥ 2 h.