Abstract
Diffusion bonding on oxygen free copper showing a low flow stress at high temperatures was carried out with changing surface roughness and delaying contact between bonding surfaces until a temperature was raised up to bonding condition. Tensile strength was increased with decreasing the surface roughness, but a fracture occurred at the bonded interface even in the specimens not observed voids. While, they fractured at not the bonded interface but the base metal with delaying contact between bonding surfaces. It was attributed to removing oxide inclusions at the bonded interface. These oxide inclusions existed at the bonded interface of the specimens whose surfaces were chemically polished prior to the bonding. Grain boundary migration across the bonded interface was generated only in the specimens given fine surface roughness and long bonding time. The behavior was scarcely depended on misorientation of grain boundaries. The fracture at the base metal was attained in the specimens retaining an original bonded interface. It would be indicated that joint strength was not affected by the grain boundary migration.
