Effect of interface microstructure on the bond strength of the diffusion welded joints between titanium and stainless steel

Diffusion bonding between commercially pure titanium and 304 stainless steel was carried out at a temperature of 950 °C for 30-120 min under uniaxial load in a vacuum. The diffusion bonds were characterized by optical and scanning electron microscopy. The diffusion zone contained different reaction bands and their chemical composition was determined using energy dispersive X-ray spectroscopy. The concentration of chemical species indicated the presence of σ, λ, χ, FeTi, β-Ti and Fe2Ti4O phases in the reaction zone and their existence was confirmed by X-ray diffraction. A maximum bond strength of ∼71% of that of titanium along with 5.8% ductility were obtained for the diffusion couple processed for 30 min due to formation of finer size intermetallics. A rise in joining time increases void generation and growth of intermetallic compounds, which are responsible for a drastic fall in the strength value.