Microstructural study on the processing and properties of high-field A15 superconducting materials
Thesis/Dissertation
·
OSTI ID:5859980
Superconducting properties of high-field A15 materials were studied in terms of the physical and chemical states of the A15 phases. The A15 materials investigated include the V/sub 3/Ga and Nb/sub 3/Al phases formed by a direct-precipitation process, the multifilamentary Nb/sub 3/Sn formed by the bronze-process, and the bronze-processed Nb/sub 3/Sn with a Mg addition. The direct-precipitation process has been found to have an intrinsically inferior critical current and lower stability, due to the large effective grain size, off-stoichiometric composition, and the high stability of BCC films between A15 grains. For the bronze-processed Nb/sub 3/Sn multifilamentary wire, microscopic examination reveals that the reacted layer consists of a three-shell composite structure. The critical current density is apparently determined by the areal fraction, grain size and composition of the central, fine-grained layer. Isothermal aging at intermediate temperatures (700-730/sup 0/C) yields that best combination of microstructural features and the highest critical current. Double-aging treatments that start at 700/sup 0/C and finish at 730/sup 0/C improve the microstructural state of the A15 layer, and enhance the critical current density by approximately 50% at fields between 10 and 15T. Magnesium addition to the bronze matrix increases the attainable critical current density (100-300%) in bronze-processed multifilamentary Nb/sub 3/Sn wires as compared to the Mg-free wire at the nearly fully reacted heat treatment conditions. The Mg segregates almost completely to the Nb/sub 3/Sn layer, and residues predominately within the A15 matrix. The most obvious effect of the Mg addition is to retard grain coarsening during growth of the A15 layer, yielding a uniformly fine-grained A15 layer.
- OSTI ID:
- 5859980
- Country of Publication:
- United States
- Language:
- English
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Microstructural study on the processing and properties of high-field A15 superconducting materials
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Wed Aug 01 00:00:00 EDT 1984
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Microstructure and critical current characteristic of a bronze-processed multifilamentary Nb/sub 3/Sn superconducting wire
Journal Article
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Wed Nov 30 23:00:00 EST 1983
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OSTI ID:6684587
An investigation on the enhancement of the critical current densities in bronze-processed Nb/sub 3/Sn
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Thu Dec 31 23:00:00 EST 1981
· Adv. Cryog. Eng.; (United States)
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OSTI ID:6238572