Critical Currents of Cu-(Nb1-xTax) 3Sn In Situ Multifilamentary Wires
Tantalum additions to the Nb core are known to considerably increase the critical current of bronze processed Cu-Nb3Sn multifilamentary wires, particularly at magnetic fields above 12 T.1,2 The present work is an attempt to reproduce this result on wires prepared by the in situ technique. 3,4 The addition of Ta as a third component, which is easily performed on bronze processed wires, introduces, however, a fundamentally new problem for the in situ process: the step from a two-component to a three- component system makes it impossible to predict the nature of the precipitates. The formation of additional phases can practically be excluded since Ta, like Nb, is nearly immiscible with Cu in the solid state,5,6 while Ta and Nb are completely miscible. The main subsisting question is whether Ta would precipitate out of the melt in its elementary state, rather than dissolve in the Nb dendrites. The measurement of Jc at high fields allows to give a qualitative answer to this question.
KeywordsCritical Current Density Graphite Crucible Composite Wire Levitation Melting Multifilamentary Wire
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