Abstract
Superconducting properties (Tc and Jc) of the in situ Cu–20Nb–Sn and Cu–30Nb–Sn composites were studied from a metallographic viewpoint.
High Tc was obtained after heat treatment at high temperature above 973 K in both composites, while high Jc was obtained after heat treatment at relatively lower temperature of 823 K . Cu–30Nb–Sn showed higher Tc and Jc than Cu–20Nb–Sn. It is considered that the decrease in Jc after heat treatment at a high temperature of 973 K is due to the coarsening of Nb3Sn filaments. True Jc at 9T, which was calculated from the highest Jc divided by the volume fraction of Nb3Sn was about 3×109 A/m2, being comparable to Jc in commercial Nb3Sn superconductors.
