Microstructure and mechanical property of brazed joints in titanium alloy and aluminum alloy combination with tin foil interlayer

Brazing of a titanium alloy and an aluminum alloy was performed in a vacuum furnace with a pure tin foil interlayer. The microstructure and mechanical property of the brazed joint were investigated as functions of parameters including post bonding heat treatment. The results indicated that Al-Ti-Sn secondary phases were present in the joining region. These secondary phases coarsened clearly with increasing temperature from 450°C to 500°C. At 450°C, the unbonded zone appeared in the interface area between the Ti alloy and the joining zone. At 500°C, some cracks and coarsened secondary phases were observed in the joint. From 450°C to 500°C, the strength of the joint gave a hill-shaped curve change. The fracture was mainly brittle fracture. As the post bonding heat treatment was applied, the interdiffusion region with about 6 μm was found in the interface zone between the Ti alloy and the joining area, the secondary phases distributed with a small and dispersed pattern, and the tensile strength of the joint was improved to a higher value. Failure mode with lots of dimples was a ductile pattern.