Manufacture, electromagnetic properties and microstructure of an 18-filament jelly-roll Nb sub(3)Al superconducting wire with rapid heating and quenching heat-treatment

In this paper, we have reported the manufacture of a novel simple-structured jelly-roll Nb sub(3)Al precursor long wire, and its electromagnetic properties and microstructure with different rapid heating and quenching (RHQ) heat-treatments. By comparing three processing methods, it is found that the rolling and drawing (RD) method is more suitable to the fabrication of kilometer-length Nb sub(3)Al precursor wire without annealing. Using homemade RHQ equipment, we have successfully carried out RHQ heat-treatment of Nb sub(3)Al wire samples with various heating conditions. Based on magnetization and magnetoresistivity measurements, the onset superconducting transition temperature, T sub(c) and upper critical field, H sub(c2) (0) of optimal Nb sub(3)Al wire reach 17.9 K-18.0 K and 29.7 T, respectively. Through microstructure and composition analysis, the Nb sub(3)Al superconductor in the optimal wire displays a typical 'layer-to-layer' structure, which comprises alternate crystalline Nb sub(3)Al and amorphous Nb layers, and the Nb sub(3)Al grains sizes are about 100nm-300nm. Furthermore, many small holes are dispersed in the Nb sub(3)Al superconductor due to the diffusion reaction from Al to Nb site. The work suggests the simple-structured Nb sub(3)Al precursor wire with RHQ heat-treatment is very promising for high-field application.