The influence of coarsening treatments upon properties of in situ Nb3Sn-Cu superconducting wire

A controlled coarsening step is shown to offer a technique for greatly extending the range of wire reductions possible in the manufacture of in situ Nb3Sn-Cu superconducting wire. Experiments have been carried out in which Cu-30 wt % Nb in situ Nb3Sn-Cu wires have been prepared employing a coarsening anneal at 750 and 1000°C prior to final reduction to wire size. Results show that coarsening treatments may be utilized to achieve optimum control of filament sizes in order to maximize Jc. Values of Jcequivalent to those of uncoarsened wires are obtained and information is presented on contact welding of Nb3Sn filaments in in situ wires.