The Interface Microstructure and Mechanical Properties of Niobium-316L Stainless Steel Explosively Welded Composite Plate

In order to manufacture stainless steel helium vessels for the superconducting radio frequency (SRF) cavities, niobium-316L stainless steel composite plates were fabricated by explosive welding technique. The microstructure and mechanical properties of the composite plates were investigated both right after explosive welding and after annealing. The microstructure measurement results demonstrated that there was not any brittle intermetallic layer formed nor any diffusion phenomenon observed after heat treatment processes. Due to the plastic deformation and work hardening near the interface, the hardness of the composite plates was higher near the bonding interface than inside the bulk metal regions. Meanwhile, ultimate tensile strength and shear strength of the composite plate reached their maximum values when the sample was annealed at 873 K for 10 h at room temperature. Charpy impact test results at liquid helium results showed that the toughness of composite plate meets the requirements from the SRF cavities' helium vessels fabrication.