Effects of heat treatments on microstructure changes in the interface of Cu/SS316L joint materials

Precipitation and dispersion strengthened copper alloys joined with 316L austenitic stainless steel are expected to be heat sink materials in the first wall and divertor of International Thermonuclear Experimental Reactor (ITER) owing to the good thermal conductivity of Cu alloys. In the present study, the effects of heat treatment on microstructural stability in the interface of CuNiBe/SS316L and CuAl25/SS316L have been investigated. In the as-received CuNiBe/SS316L joints, voids were observed at the interface, and in the stainless steel side near the interface. But in the CuAl25/SS316L joints, voids were observed only in the Cu side near the interface. These voids would have a significant effect on the mechanical properties of joints. The results of annealing experiments showed that the microstructures in the interface of both types of joints were thermally stable during annealing at 573 and 673 K for 100 h.