Influence of Ge addition on phase formation and electromagnetic properties in internal tin processed Nb/sub 3/Sn wires

In order to investigate the effect of Ge addition to the Cu matrix on the microstructure and the critical current density, four kinds of internal tin processed Nb/sub 3/Sn strands with pure Cu and Cu-0.2, 0.4, 0.6 wt% Ge alloys were drawn to 0.8 mm diameter. The microstructure and critical current of internal tin processed Nb/sub 3/Sn wires that were heat treated at temperatures ranging from 680/spl deg/C to 740/spl deg/C for 240 h were investigated. The Ge addition to the matrix did not make workability worse. A Ge rich layer in the Cu-Ge matrix suppressed the growth of the Nb/sub 3/Sn layer and promoted grain coarsening. The greater the Ge content in the matrix, the fewer the net J/sub c/ result after Nb/sub 3/Sn reaction heat treatment. There was no significant variation in J/sub c/ observed with heat treatment temperature ranging from 680/spl deg/C to 740/spl deg/C.