Influence of Ge addition on phase formation and electromagneticproperties in internal tin processed Nb3Sn wires

摘要

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 Nb3Sn 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 Nb3Sn wires that were heat treated at temperatures ranging from 680°C to 740°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 Nb3Sn layer and promoted grain coarsening. The greater the Ge content in the matrix, the fewer the net Jc result after Nb3Sn reaction heat treatment. There was no significant variation in Jc observed with heat treatment temperature ranging from 680°C to 740°C