Effects of residual stress on fracture strength of Si3N4/stainless steel joints with a Cu-interlayer

The variation in fracture strength of a brazed Si3N4/Cu/steel joint was compared with the change in residual stress as a function of the Cu-interlayer thickness that was used. The higher residual stress and the lower measured fracture strength for the joint, using a 0.1 mm thick Cu-interlayer, were ascribed to the entire dissolution of the Cu-interlayer into the brazing alloy. The finite element analysis of residual stress, which considered the microstructure at the interface region, could explain the fracture behavior for the brazed joints, which is dependent on the thickness of the Cu-interlayer.