Beryllium-copper joining techniques for use on plasma-facing components

Several technologies are being evaluated as methods of joining beryllium to copper for plasma facing components in fusion reactors. The mechanical and microstructural properties of these bonds are reviewed and compared with the requirements for the application. The prime candidate for the plasma facing material is S-65C grade beryllium. At present three copper alloys are being considered for the structural substrate and include an oxide dispersion strengthened copper (CU-Al2-O3) and two precipitation strengthened copper alloys (CuCrZr and CuNiBe). The three joining technologies presented in this study include inertia welding, electroplating and brazing. In the case of the brazed bond, the braze alloy is selected based on compatibility with the reactor design. Several brazing candidates have been discounted because of their transmutation products in the high neutron flux environment. The braze alloys used in this study were aluminum base. Of paramount concern in all methods of joining was the elimination of a reaction between beryllium and copper to form an intermetallic phase, the presence of which would severely degrade bond ductility