Interfacial microstructure evolution and mechanical response of TC19/ Ti150 dissimilar joints obtained by diffusion bonding

The structure made by dissimilar titanium alloys can meet the differentiated requirements of performance for different parts, fully exerting their performance advantages during operation respectively, which holds significant technological and economic value. Here, we used diffusion bonding (DB) method to connect TC19 and Ti150 dissimilar titanium alloys in the temperature range of 810 degrees C-900 degrees C, and investigated the morphology, forming mechanism, deformation behavior and mechanical properties of the joints. The study showed that the interfacial voids disappeared with the increase of temperature, and the interfacial characteristics gradually evolved from the initial straight shape to a curved shape. The original bond line transformed into (3TC19/alpha Ti150 phase boundaries (PBs) and high-angle grain boundaries (HAGBs) formed by alpha TC19 and alpha Ti150. No harmful intermetallic compounds were formed on the interface. The joint formation can be considered as a combination of three behaviors: plastic deformation, elemental diffusion and interfacial grain boundary migration (IGBM). In addition, it was observed that dislocation slip was the main deformation behavior of the joints. The dislocations generated in the both matrices were obviously accumulated at the interface during tensile deformation of the specimen, and the bonding interface hindered the dislocation transfer between two substrates. The room temperature uniaxial tensile results exhibited that the joints bonded at 810 degrees C and 840 degrees C were broken at the interface, showing poor mechanical properties caused by holes and straight interface. And yet the joints bonded at 870 degrees C and 900 degrees C occurred fracture on the Ti150 matrix. The strength of joints was comparable to that of the Ti150 matrix, indicating that the two dissimilar titanium alloys achieved a reliable bonding. This work provides valuable inspiration for the diffusion bonding process of titanium alloys with different microstructures.