Engineered Dual NbTa Barriers for Higher Jc Nb3Sn Superconductors

The tantalum (Ta) diffusion barrier in advanced Nb3Sn superconductors often develops a failure mode during wire drawing. In this mode, the Nb and Ta layer deforms non-uniformly, leading to a rough interface with adjacent copper. The non-uniform deformation of these layers can lead to premature wire breakage, breaches in the barrier, and contamination of the copper stabilizer by tin (Sn). This project will demonstrate that a dual NbTa layer, made from the severe plastic deformation of Nb and Ta, exhibits improved co-deformation behavior with pure Cu in advanced Nb3Sn superconductors. Phase I will demonstrate the improved microstructural uniformity and superior mechanical property characteristics of Nb and Ta sheets, which are processed and rolled using equal channel angular extrusion (ECAE), compared to commercially available materials. Also, an improved barrier performance, using a dual NbTa barrier concept, will be demonstrated in composite wires. During Phase II, a second-generation dual NbTa barrier design with fine-grained Nb and Ta components will be fabricated and tested in an experimental Nb3Sn superconductor. Commercial Applications and other Benefits as described by the awardee: This technology should find application in the production of Nb and Ta sheets for use in Nb3Sn superconductors.