Abstract
A commericially pure titanium has been diffusion-bonded to iron and steels of various carbon contents ; low carbon steel with 0.01%C(ULC), mild steel with 0.19%C(S20C) and spheroidal graphite cast iron with 3.75%C(FCD). The tensile strength of joints bonded below 900°C was hardly influenced by the carbon content, and increased with the rise in bonding temperature. Above 900°C, however, the strength of the Ti-to-ULC joint showed a constant value, that of the Ti-to-S20C joint decreased, and that of the Ti-to-FCD increased with the rise in bonding temperature. The interlayer forming along the bond interface consisted only of TiC in the Ti-to-FCD joint and of TiFe and TiFe2 in the Ti-to-ULC. Since Ti and Fe diffused over much longer distances in the Ti-to-ULC than in the Ti-to-FCD, the TiC layer may be considered to interfere with the interdiffusion of Ti and Fe, and consequently to suppress the formation of TiFe and TiFe2 which decrease the joint strength more seriously than TiC. The interlayer in the Ti-to-S20C consisted of TiC as well as TiFe and TiFe2. The coexisting carbide and intermetallic compounds in the interlayer, seems to reduce the joint strength to a more extent than those formed individually.
