Brazing mechanism and interface characteristics of Ti/Al brazed alloys were investigated at temperature of 620℃. 1050Al and cp-Ti were used for the base metals, and 100μm thick Al-10Si-1Mg alloy foils were used for the filler metal. The adhesive shear test, X-ray diffraction analysis and microstructure observations were performed. The bonding process of Al/filler was divided into four steps. The first step was the wetting of molten filler metal on the surface of Al. The second step was the removal of oxide film on the surface of Al. The third step was the isothermal solidification of filler metal by the diffusion of Si from filler metal into base alloys. Finally, the homogenization of Si at the bonded region was occurred. The bonding process of Ti/filler consisted of the formation of intermetallics and the growing of intermetallics by the diffusion of solute atoms. The intermetallic layers were formed at Ti/filler interface and the composition of the intermetallics were identified as Al5Si12Ti7 and Al12Si3Ti5. The Si content of Al base metal was identified by WDS. The Si content in filler metal decreased due to the diffusion of Si into Al base metal and into the intermetallic layers with increasing the brazing time. The thickness of molten filler metal layer decreased with increasing bonding time by the decrease in Si content in molten filler metal. The bond strength of Al/Ti brazed joint was measured by adhesive shear test. The bond strength profile with increasing the brazing time was divided into three regimes. In regime I, the bond strength of the brazed joint increased rapidly up to 73MPa with increasing the brazing time up to 7min. In regime II, the bond strength increased slowly or nearly constant with increasing the brazing time up to 30min. In regime III, the bond strength decreased with increasing the brazing time up to 2hours. The bond strength peak of 84MPa was observed at the brazing time of 30min in regime II. The oxide film was existed and the fracture was occurred at the Al/filler interface in regime I. The oxide film was removed and the thickness of intermetallic layers was less than 10μm in regime II. The cracks were initiated near intermetallic layer and the fracture was occurred at intermetallics/Al interface in regime III.
