The conversion of the bronze matrix into the stabilizing Cu in Nb3Sn wires

We have found the condition to remove Sn from bronze by oxidation. The reactions are the oxidation of Sn at the surface of bronze and the diffusion of Sn from inside bronze toward the surface. The reaction rate is dominated by the later. This technique has been adapted to the internally stabilized Nb3Sn wires. It has been expected that the removal of Sn is perfect and the volume fraction of Cu increases from 19.2% to more than 65%. However, Sn removal enhances the conductivity of the wire at low temperature by no more than 40%. The theoretical estimation about the volume fraction of each component after the reactions suggests that 6-10% of volume fraction of Kirkendall voids remain in the Cu matrix.