Current characteristics and microstructure in a multifilamentary Nb-37Ti-22Ta superconductor

The 210-filamentary superconductor based on Nb37Ti-22Ta, wt.% alloy was obtained by using the electric are melting and deformation processing. During alloy drawing we used four isochronal intermediate heat treatments at the temperature 425 degreesC. The total heat treatment duration was varied from 50 to 1000 hours. The true plastic strain value between heat treatments was 0.4 and after the final treatment was 3-5. The kinetics of phase transformation in the ternary alloy was investigated by the method of transmission electron microscopy. The J(c) value increases with an increasing quantity of the precipitated alpha-phase in medium magnetic fields. The J(c) (5 T, 4.2 K) value reaches 3000 A/mm(2) or more. In high fields, J(c)(10.4 T, 2.05 K) for the given superconductor was equal to 1600 A/mm(2). The parameters responsible for the shape of pinning force curve are determined for different treatment conditions.