Preparation and Properties of In Situ Prepared Filamentary Nb₃Sn-Cu Superconducting Wire

Abstract

Several years ago we began a project to make superconducting wire by directionally solidifying Cu-Nb binary alloys so as to give an aligned array of Nb dendrites in a copper matrix. These composites were to be drawn to wire, coated with tin and heat treated to produce aligned Nb₃Sn filaments in a bronze matrix. Initial studies, however, showed that directional freezing was not required to produce alignment of the Nb dendrites; the wire drawing process itself produced excellent alignment of the initially random array of Nb dendrites produced by conventional casting techniques. This method of fabricating Nb-Sn-Cu wire, which has been developed independently by Bevk et al.¹ at Harvard and by Roberge and Foner et al.² at the Hydro-Quebec Research Institute and MIT, has come to be called the in-situ technique for preparing Cu-Nb-Sn superconductor wire. In this paper we present a brief review of our results at the Ames Laboratory on the development of this in-situ process.