Effects of Bonding Time on Microstructure and Mechanical Properties of Ti3Al/Ti2AlNb Joint Prepared by Transient Liquid Phase Diffusion Bonding

Using Ni-Ti duplex foils as joining materials, Ti3Al alloy was bonded to Ti2AlNb alloy by transient liquid phase (TLP) diffusion bonding at 990 degrees C under low bonding pressure (0.1 MPa). The effects of bonding time on the microstructure and mechanical properties of Ti3Al/Ti2AlNb joint were analyzed, as well as the interfacial evolution and forming mechanism of the TLP joint were studied. Results show that the Ti3Al/Ti2AlNb alloy joints with typical interface structure of Ti3Al | Al0.5Nb0.5Ti3 | residual Ni | NiTi | NiTi2 | residual Ti | Al0.5Nb0.5Ti3 | Ti2AlNb can be formed. In addition, with the extension of bonding time, the shear strength of the joint first increases and then decreases, and the maximum shear strength, up to 167 +/- 12 MPa, of the Ti3Al/Ti2AlNb alloy joint can be achieved when the bonding time reaches 60 min. The joint fracture, characterized by brittle fracture, mainly occurs at the NiTi2 layer adjacent to the Ti2AlNb/Ti interlayer and extends to the Ti interlayer.