The Effects of Intermediate Layer and Surface Nanocrystallization on the Vacuum Diffusion Bonding of Commercially Pure Titanium

Using cooper foil as intermediate layer, commercially pure titanium (CP-Ti) was vacuum diffusion welded after surface nanocrystallization. The effects of the interlayer and SNC treatment on the bonding state were discussed thereafter. The results showed that about 10 μm nano-structured surface layer was achieved on CP-Ti. Well bonded joint could be obtained by two original CP-Ti samples welded directly at the conditions of 950°C welding temperature and 5 MPa pressure. Excellent bonding between nanocrystalline Ti and cooper substrate was achieved at 850°C but lots of cavities were observed on the interface when welded at the same temperature as that for two Ti substrates. Surface nanocrystallite utilization could play a role in promoting interface diffusion procedure by surface atoms activation and large amount of diffusion channels. Cu substrate increased the contact area of interlayer to prevent the possible influence of induced surface roughness on diffusion bonding formation.