Superconductivity Critical Current Densities in Ti–V Alloys

Abstract

Specimens of Ti-20% V alloy were heat treated to a β-solid-solution condition and then aged for several fixed times and temperatures below the β transus. X-ray and electron diffraction were used to determine the composition and distribution of the metallurgical phases produced by the aging treatments. These data were correlated with measurements of the superconducting transition temperature and critical current density. In order for these materials to carry resonable supercurrent densities at 4.2°K, it is necessary that the matrix be rich enough in V for the transition temperature to be greater than 4.2°K and that there be present an array of flux-pinning sites. It was found that aging temperatures of 400°, 500°, or 600°C were required to insure the first condition. The flux pinners produced were ω particles in the case of the 400°C treatment and α precipitates in the case of the 500° and 600°C treatments. In many specimens, the superconducting-to-normal transition at a given value of applied field was spread out over a wide range of transport current rather than being abrupt as is usually the case.