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 Nb
3
Sn-Cu superconducting wire. Experiments have been carried out in which Cu-30 wt % Nb in situ Nb
3
Sn-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 J
c
. Values of J
c
equivalent to those of uncoarsened wires are obtained and information is presented on contact welding of Nb
3
Sn filaments in in situ wires.