Long lengths of multifilamentary Nb Ti composites, which comprise several thousands. 5 to 1 micron-diameter filaments, have been manufactured. These composites, with a Cu-Cu Ni mixed-matrix and some of them with pure Cu Ni between the filaments, carry hight current densities up to 1.95 105 A/cm2 at 5 Teslas. Their structure provides a good magnetic stability and leads to strongly reduced 50 Hertz losses. These results allow to consider alternators with superconducting rotor and armature windings and, in a general way, they open very new prospects for industrial applications of superconductivity in fast pulsed magnets and in A.C. current devices
Absfracf--The formation of deleterious intermetallic compounds is strongly hindered by the niobium coating of the filaments. This paper deals with the problem of determination of a minimum of thickness for this barrier. The location of the primary compounds to form as well as the mechanisms of permeation of the barrier are thoroughly investigated. Due to these results, the relative importances of the phenomena of mechanical alloying and of thermal diffusion are determined. The whole of this work leads to the estimate of a minimum of thickness for the Nb layer at the beginning of the last heat treatment. The meaning of this result is finally reconsidered because of the subsequent mechanical damage of the barrier.
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