Diffusion bonding of alumina dispersion-strengthened copper to 316 stainless steel with interlayer metals

Diffusion bonding of alumina dispersion-strengthened copper (DS Cu) to 316 stainless steel was carried out with interlayer metals such as Au, Cu and Ni foil in order to investigate the influence of the interlayer metals and bonding conditions on strength of the joints. The tensile strength of joints with an Au interlayer was superior to those with Cu and Ni interlayer metals and similar to that of Ds Cu base metal. The tensile strength of joints with a Cu and Ni interlayer was less than that of immediate diffusion bonding joint for the Ds Cu to 316 stainless steel. The Charpy-absorbed energy of the Au interlayer joint increased up to 50% of Ds Cu, while that of the immediate diffusion bonding joint was only 20%. Concerning the microstructure of the Au interlayer joints, intermetallic compounds consisting of B, Fe and Cr were observed in the Au interlayer. For the Ni interlayer joints, Kirkendall voids were formed in the DS Cu near the interface where the specimen fractured. The specimens with the Cu interlayer fractured at the interface between Ds Cu and Cu interlayer. It is suggested that the degradation of the strength of the joints with the Cu interlayer is attributed to the diffusion rate between the Cu interlayer and the DS Cu.