Effect of bending and thermal treatment on CuCrZr/316 L interface for flat-type divertor target by explosive welding

Abstract

The application of copper alloy in divertor faces great challenges. The explosively welded CuCrZr/316 L composite plate, which maintains high structural strength while ensuring efficient heat transfer, is commonly employed as a heat sink material in divertor targets. In the development of continuous closed V-shaped structure of divertor target, which is beneficial for plasma detachment, the composite material can provide sufficient heat transfer performance when the bonding interface is bent to a radius of R60mm. However, exposure to high temperatures of 830 °C can induce leakage along the bonding interface in the bent region. This study investigates the bonding interface of explosively welded CuCrZr/316 L composite plates under different bending radii and thermal treatments through tensile tests, microhardness measurements, microstructural characterization, and elemental diffusion analysis, thereby identifying the root cause of leakage. It is found that performing a solid solution at 970 °C prior to bending induces recrystallization in both CuCrZr and 316 L, eliminating the work hardening introduced by explosive welding. In the subsequent experiments involving solid solution followed by bending to a radius of R60 mm, the bonding interface successfully withstood a helium pressure test of 4.5 MPa.