High Critical Current Superconducting Titanium-Niobium Alloy

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Abstract
The stabilization of transport current in a high field Ti‐Nb alloy by metallurgical heat treatment was investigated. Solid‐solution annealing of the alloy, followed by nucleation and growth of a second‐phase precipitate, was found to have a pronounced influence on the ability of the alloy to carry high transport current in high magnetic fields. The precipitate was most effective in the early stages of growth. Overaging resulted in reduced values of critical transport current density. Aging of a Ti‐20.7 at. % Nb alloy for ¾ to 6 h at 400°C yielded a critical current density in excess of 105 A/cm2 at 4.2°K in a 30‐kG applied magnetic field. The same alloy in a solid solution condition carried less than 104 A/cm2 at the same temperature and field. The upper critical field (Hc2) of the aged alloy was found to be 128 kG at 1.2°K.