Effect of reaction products on mechanical properties of diffusion bonded of titanium to 304 stainless steel with Cu interlayer joints

In present study, pure copper was used as an interlayer of the diffusion bonded joints between commercially pure titanium and 304 stainless steel. The process was carried out at 900°C for 30–150 minutes in steps of 30 minutes under 3MPa uniaxial load in vacuum. Microstructures of the bonded assemblies were observed in optical and scanning electron microscopes. The study exhibits the presence of different reaction layers in the diffusion zone and their chemical compositions were determined by energy dispersive spectroscopy. Formation of reaction products in diffusion interfaces were confirmed by xray diffraction technique. The maximum tensile strength of ∼322MPa (∼101% of Ti) and shear strength of ∼254MPa (∼86% of Ti) along with 8.4 % ductility were obtained for the couple bonded for 60 minutes and due to the rise in bonding time up to 90 minutes, bond strength drops marginally. With a further increase in joining time, the bond strength drops gradually due to the increase in the width of Fe-Ti base reaction products. Observation of fracture surfaces in SEM using EDS indicated that fracture takes place through the SS-Cu interface for all bonded samples.