Development of Multifilamentary Superconductors Containing Nb-40wt%Ti-18wt%Ta and Nb-41wt%Ti-28wt%Ta Ternary Alloys

Multifilamentary superconducting materials containing ternary alloys have been manufactured and their properties studied at 4.2K and 1.8K. Two compositions, Nb-40wt.%Ti-18wt.%Ta and Nb-41wt.%Ti-28wt.%Ta were selected as they appeared to offer the maximum enhancement of Hc2’s over the binary alloys at both 4.2K and 2.0K, respectively. Superfluid helium is now being considered for an increasing number of large devices. Thus, the study of these highly ductile ternaries at 1.8K to 2K is very important. Three 50.8 mm diameter multifilamentary billets were made from two ternary alloys and the Nb-46.5wt.%Ti binary alloy which provided a base line for comparison purposes. Critical current densities, (Jc’s) for all materials after different thermomechanical treatments were measured at 4.2K, 2.0K and 1.8K. The upper critical fields of three alloys at 4.2K and 2.0K were determined from the extrapolations of Jc’s to zero, and termed Hc2*. Volume fractions and sizes of α-Ti precipitates immediately after the heat treatments were examined. Critical temperatures, (Tc’s) for all alloys were also measured. The results of the properties measured will be discussed in this paper.