Soldering, Brazing and Diffusion Bonding TECHNOLOGY of ADVANCED Materials In HIT

Al₂O₃ and Ti6Al4V, Cu and Cu, Ti and Ti6Al4V were successfully joined by brazing, soldering and diffusion bonding. Joints microstructure was investigated by scanning electron microscope (SEM), transmission electron microscope (TEM) and energy dispersive spectrometer (EDS). Interfacial reactions and joining mechanism were analyzed and joining parameters were optimized. The mechanical properties of the joints were measured by mechanical testing machine. Results indicate that TiB whiskers could adjust the mismatch of CTE between Al₂O₃ and Ti6Al4V to decrease the residual thermal stress of Al₂O₃/Ti6Al4V joints. When the brazing layer contained 40vol.% TiB whiskers, the joint obtains the highest shear strength 77.9 MPa at 900°C/10 min. The mechanical strength of Sn-58Bi solder with different reinforcement (CNTs, 9Al₂O₃·2B₂O₃), which prepared by either ball milling and low temperature melting process or mechanical mixing method, was better than Sn-58Bi matrix owing to reduce of Sn-rich segregation and the grain refinement. Both the addition of CNTs and the whiskers could improve the wettability of the composite solder. The increasing soft bH phase enhanced the local plastic deformation of hydrogenated titanium alloys, and the voids disappeared at the diffusion bonding interface. Together with the dehydrogenation reaction heightened the element diffusion and the surface activity, which led to the acceleration of the diffusion bonding process.