Development Studies on Powder Processed Nb sub 3 Al Superconducting Wire

摘要

Results are reported of recent developmental research on powder-processed Nb sub 3 Al superconducting wire. The development of a good superconducting wire requires the control of at least two distinct aspects of the A15 phase: its internal composition and state of order, which determine its inherent superconducting characteristics, and its microstructural distribution within the wire, including such factors as its volume fraction, grain size, and continuity, which determine the peak critical current a phase of given internal state can transport. The research reported concentrated on the microstructural characterization of powder-processed wire and on the modification of processing to improve the microstructure and to enhance the inherent superconducting characteristics of the A15 phase. The results show that it is possible to obtain very promising values of the critical temperature and high-field critical current density in powder-processed Nb sub 3 Al superconducting wires. They suggest, moreover, that much better properties are obtainable. Microstructural analysis of the reacted samples reveals a fine, complex microstructure. Its internal characteristics are not fully understood, but it responds to appropriate variations in heat treatment with significant favorable changes in superconducting characteristics. The further clarification of the microstructure should permit a choice of powder characteristics, wire processing, and heat treatment leading to very good superconducting characteristics. (ERA citation 07:022795)