Critical current density and n-value of NbTi wires at low field

The manufacturing process of NbTi wires for lower field applications is optimized concerning both the number of heat treatments and the final true strain, the strain of a wire from the wire diameter at the last heat treatment to the final diameter. The sample wires were made from Nb 54wt%Ti alloy and were manufactured to vary the number of heat treatments (0, 1, 2, and 3) and the final true strain (0 to 3). One of these samples, which had one heat treatment and drew with the final true strain of 0.33, achieved J/sub c/ of 3360 A/mm/sup 2/ and n-value of 111 at 3 T. This J/sub c/ is as good as a J/sub c/ of the wires made from conventional materials and this n-value is 3 times as large as the n-value of wires mentioned above. Furthermore, the n-value at 3 T and the minimum value of the cross-sectional area of each filament show a correlation coefficient of 0.73.<
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