Superconducting critical current densities of pure and alloyed (Ti) Nb3Sn multifilamentary wires by the expanded-metal process

The critical current densities Jc(H) at 4.2 K and up to 19 T were measured for a number of pure and alloyed (with Ti) Nb3Sn multifilamentary wires which were fabricated by the expanded metal process. The critical current density (including the areas of Nb3Sn, the Cu-Sn alloy matrix and the Ta barrier) of the pure Nb3Sn wire at 10 T was essentially equal to the value for conventionally processed Nb3Sn wires. However, it rapidly decreased with increased magnetic fields. Although the addition of small amounts (∼0.8 and ∼ 1.6 wt% Ti) to the Nb filaments decreased the values of Jcat 10 T, they did not decrease with the increasing field as rapidly as is the case for the pure Nb3Sn. The additions of Ti slightly decreased the amount of tensile strain on the wire required to achieve a maximum in Jc(8 T) when compared to that required for the pure Nb3Sn. However, this amount was higher than that for a similar Nb3Sn wire which was conventionally processed.