Notch toughness evaluation of diffusion-bonded joint of alumina dispersion-strengthened copper to stainless steel

Tensile strength of the diffusion-bonded (DB) joint was as large as that of alumina dispersion-strengthened copper (DS Cu), however, the Charpy absorbed energy of the joint was considerably lower than that of DS Cu. Instrumented Charpy impact test and slow-bend Charpy test of the DB joints were performed to clarify the degradation of Charpy absorbed energy. Elasto-plastic analyses were also carried out in order to study the deformation behavior of the tensile and Charpy V-notched specimens for the DB joints. As a result, the fracture behavior of the impact and slow-bend tests was almost the same. Elasto-plastic analyses showed that the maximum strain occurred at the DS Cu apart from the interface for tensile specimen, however, the strain concentrated at the DS Cu near the interface for the Charpy notched specimen. This strain concentration arose from the mechanical heterogeneity between stainless steel and DS Cu in the bonded zone and can be attributed to the degradation of the absorbed energy of the DB joints.