Microstructural Properties and Magnetic Testing of Spot-Welded Joints Between Nb-Ti Filaments

The production of persistent-mode joints between Nb-Ti conductors remains an important problem in the field of superconducting magnets. Several researchers have demonstrated spot welding (resistance welding) as a technique capable of yielding superconducting joints directly between Nb-Ti filaments. In this study, the characteristic microstructural features associated with spot-welded joints between both multifilamentary and monofilamentary Nb-Ti wires are presented. Some initial measurements of the current-carrying ability of a monofilamentary joint have also been made by a novel magnetic technique. The suitability of spot welding for commercial magnet manufacture is discussed.