Mechanical Strength Evaluation of the Internal Matrix Reinforced Nb3Sn Multifilamentary Wires Using Cu–Sn–In Ternary Alloy Matrix

We investigated the simple internal reinforcement method using special reinforcement ternary bronze alloy matrix on the bronze processed Nb₃Sn wire. The Cu-Sn-Zn ternary alloy matrix was transformed to the (Cu, Zn) solid solution after Nb₃Sn synthesis based on the solid solution strengthening mechanism. For the further mechanical strength improvement, we focused on the Indium (In) as the more effective solute element for the “internal matrix strengthening”, and succeeded to fabricate the bronze processed Nb₃Sn multifilamentary wire using various Cu-Sn-In-(Ti) ternary alloy matrices. Changes of the Vickers hardness before and after Nb₃Sn synthesis and the transport critical current (Ic) under the uniaxial tensile deformation were evaluated. Vickers hardness of the matrix after Nb₃Sn synthesis on the Cu-Sn-In ternary alloy matrix samples was higher compared with the conventional bronze and the Cu-Sn-Zn ternary matrix samples. On the other hand, the tensile stress obtained to the maximum peak Ic value on the Cu-Sn-In ternary alloy matrix sample was estimated to approximately 265 MPa, and this value was much higher than those of the Cu-Sn-Zn ternary matrix and conventional bronze processed samples. We found that the In element would become more attractive solute element than Zn element for the internal reinforcement ternary matrix.