Dissimilar diffusion bonding behaviour of Ti₂AlNb alloy and TiBw/Ti64 composites using the Ti interlayer

The Ti₂AlNb alloy and TiBw/Ti64 composites were successfully bonded using a Ti interlayer at 900°C–1050°C for 20–80 min. The interface of the joints showed a layered microstructure. Moreover, the width of the diffusion zone gradually increased from 30 to 58 µm owing to sufficient atomic diffusion and phase transition at higher bonding temperatures with longer bonding times. The elemental concentration gradients caused by atomic diffusion promoted the precipitation of the O phase (Zone I) and the growth of the lamellar α phase (Zone II). A well-bonded joint was obtained and showed the highest shear strength of 460.9 MPa. Microcracks emerged in the diffusion zone and propagated into the TiBw/Ti64 substrate during the shear test, and the fracture mechanism inside the composites was intergranular ductile fracture mode.