Bronze Processed Nb₃Sn Multifilamentary Wires Using Various Cu-Sn-Zn Solid Solution Strengthened Bronze Alloy Matrices

Abstract

In the magnetic confinement type fusion reactor, we thought that the high critical current density ( J c ) performance Nb 3 Sn wire will become the first candidate material for the future fusion magnet system due to its established industrial mass production and its technical achievements. However, the degradation of transport J c property due to the high mechanical and thermal strains on the practical Nb 3 Sn wire is a serious problem to apply for the future fusion magnet to be operated under higher electromagnetic force environment. We developed the new bronze processed Nb 3 Sn wire using the Zinc (Zn) solid solution high Sn content bronze (Cu Sn Zn) alloy matrix for improvement of the mechanical strength by the solid solution strengthening. We also confirmed that the Zn promoted to diffuse between Nb and Sn elements, and that Zn homogeneously remained in the matrix after the diffusion reaction. In the Nb 3 Sn wires with various Cu Sn Zn (Ti) alloy matrices, the non Cu J c value was increased by the two stage heat treatment, and the maximum non Cu J c values under the external magnetic fields of 15 T and 18 T at 4.2 K were obtained about 420 and 160 A/mm 2 . The degree of J c enhancement due to the two stage heat treatment was estimated 30 higher compared with one stage heat treatment. Change in the microstructure and the non Cu J c enhancement due to the two stage heat treatment on the Nb 3 Sn multifilamenatry wire with various Cu Sn Zn alloy matrices were reported.