MECHANICAL TESTS OF DIFFUSION BONDING JOINTS OF ALUMINA DISPERSION-STRENGTHENED COPPER TO 316 STAINLESS-STEEL FOR FUSION-REACTOR DIVERTORS

Joints of alumina dispersion strengthened copper (DS Cu) to 316 stainless steel are expected to be used for cooling pipes of the divertor in the ITER. In this study, solid state diffusion bonding of DS Cu to 316 stainless steel had been carried out to investigate the influence of the bonding conditions on the strength of the joint, where the bonding parameters were temperature, pressure and hold time. Tensile and Charpy impact tests of the joint specimens and the base metals were performed to evaluate the strength. The bonding temperature had more remarkable effect on the strength of the joint than the pressure and the hold time. The tensile strength of the joint, which was obtained at the bonding temperature of 1, 173K and pressure of 4.8 MPa, was almost the same as that of DS Cu. The absorbed energy of the joint was smaller than that of DS Cu. However, it increased with increasing temperature. The DS Cu was subjected to recovering and softening during the bonding heat treatment and consequently its proof stress was reduced by 30% at 1,273K. The softening caused the significant compressive deformation during the bonding at both high temperature and high pressure.