Clad materials consisting of aluminum and titanium plates were produced using the vacuum roll bonding method. This method produces an excellent bond without the intermetallic phase formation observable with conventional optical microscope. Bond interfacial structures in the Al/Ti clad material were observed by TEM, and the bonding mechanism were discussed.
Tensile fracture occurred in the aluminum base metal of the clad material on the tensile test and the maximum tensile strength was 95 MPa. In addition, no cracks near the bonded zone were observed in the tensile fractured specimen. Nano-crystals and ultra fine-crystals were observed within the bonded zone using TEM. Within the ultra fine-crystal zone, the compositions of Al and Ti were approximately 80 and 20 at%, respectively. Precipitates those identified as a super lattice structure of the L12 type and an intermetallic phase TiAl3 (D022 type), which are nano-meter size particles, were observed within the ultra fine-crystal zone having Al solid solution (FCC crystal) supersatulated with Ti. The bonding mechanism of aluminum to titanium on the vacuum roll bonding method can be considered that very small thin regions of aluminum surface to be bonded are melted by frictional heat due to the great relative sliding between aluminum and titanium plates during the roll bonding. After that the bonded zone is cooled rapidly due to the diffusion of the heat from the bonded zone toward each base metal and rolls, therefore, the nano-crystals and the ultra fine-crystals are formed in the bonded zone.
