Manufacture of Fine-Grained Niobium Bar

The commercial fabrication of fine-filament superconducting Nb3Sn wire has inherent problems stemming from large grains in the starting Nb material. Current severe plastic deformation (SPD) techniques can eliminate the problem by producing small grains in the large cross section Nb bars used for wire manufacture. However, such processing yields only a small amount of fully refined material, due to unworked billet end effects. This project will develop technology to improve the yield by developing new, low-cost deformation strategies. In Phase I, several new deformation routes tobulk Nb will be tested, Cu-Nb composite wires with fine-grained Nb will be fabricated, and the cost of tooling and scale-up will be estimated. The resulting tooling will be used to produce large fine-grained bulk Nb bars for wire drawing experiments in Phase II. Commercial Applications and other Benefits as described by the awardee: Lower cost Nb3Sn superconductor wire should enable the manufacture of higher field magnets for high energy physics applications such as particle accelerators. The approach also should be directly applicable to the fabrication of other materials, including Ta, Ti, interstitial free steel, and superalloys.