Novel High-Tin Bronze and Nb3Sn Multifilamentary Wires

Abstract

We developed a method for manufacturing a high Sn concentration bronze material with high ductility. The high-Sn bronze was used to produce multifilamentary wires, and their characteristics were evaluated. To increase the Sn content of the bronze and ensure ductility, the δ-phase (Cu <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">41</sub> Sn <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> ), which is a eutectoid when the Sn content is greater than the Cu-Sn solid-solution limit, was replaced with a ternary compound by the addition of Ti. The compound was further refined by hot forging to develop ductility. In this study, 1615-filament wires were produced using the high Sn concentration bronze and a commercial bronze for comparison. Each wire was heat treated with different conditions, and their superconducting properties were evaluated. The area ratio of the Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn phase was higher with the high-Sn bronze alloy irrespective of the heat-treatment temperature. The critical current density was improved for the high-Sn bronze for heat treatment at 625 °C or lower, but when the treatment was performed at 650 °C, the Ti concentration in the Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn phase exceeded 2.0at% and the upper critical magnetic field deteriorated dramatically.