Superconducting properties of a liquid-infiltration Nb-Nb3Sn composite formed during a low-temperature reaction

Abstract
A powder metallurgy based ‘‘liquid‐infiltration’’ method was used to produce multifilamentary Nb‐Sn composite wires. New heat treatments combining relatively low‐temperature aging (≤800 °C) and long reaction time (≥ one day) were used to form superconducting A15 Nb3Sn. This heat treatment can be used for large conductors and practical magnets. Transmission electron microscopy studies revealed that the A15 Nb3Sn was formed in fine filaments which were embedded in the ductile Nb matrix. Small, equiaxed A15 grains extended across the reacted filament. A Tc onset of 17.9 K with a 0.4‐K transition width was obtained. Excellent high‐field critical currents, overall Jc’s ≥104 A/cm2 in a field of 18 T at 4.2 K, were achieved.