Suitability of NbTi containing up to 2 Wt.% Ta for use in fabrication of superconductors

Procurement specifications for the widely used superconducting alloy Nb46.5Ti have a maximum Ta content limitation of 1000 ppm by weight. To study the effect of up to 2% Ta by weight in a NbTi alloy, three Ta-modified Nb46.5Ti ingots containing 0.5, 1 and 2 wt.% Ta nominal were produced. Fabricability of the modified alloys compared to standard Nb46.5Ti during normal fabrication for 0.125 inch diameter wire is discussed. At 0.125 inch diameter, a portion of each of the four types of wire was clad with OFHC copper and drawn to final composite diameters of 0.010 inch and 0.004 inch. Results of metallurgical studies conducted on in-process material are discussed. Results of short sample tests to determine critical current density for the 0.010 inch and 0.004 inch monofilament samples, including the standard Nb46.5Ti alloy for comparison, are presented.