Layer growth and microstructure in Nb/sub 3/Sn multifilamentary superconducting wire
Columnar Nb/sub 3/Sn grains are present adjacent to the Nb interface for all initial Nb/sub 3/Sn layer thicknesses. Stress relief mechanisms, operating to relieve stresses induced by the transformation of Nb to Nb/sub 3/Sn, are predominantly responsible for the microstructure of the reacted layer. Both time dependent (diffusive) and time independent (non-diffusive) mechanisms operate. Thus the Nb/sub 3/Sn formation rate affects the final microstructure. A fast formation rate results in an equiaxed morphology. The addition of Mg to the starting Cu-Sn in bronze-route multifilamentary conductors refines the final Nb/sub 3/Sn microstructure effecting higher critical current densities, Wu et al. However, the grain refining effect, and concomitant increase in J/sub c/, is indiscernible when the N/sub 3/Sn formation rate is such that a fine equiaxed morphology results. The addition of Ti to the starting Nb in bronze-route multifilamentary conductors raises the H/sub c2/ of the Nb/sub 3/Sn and thus the critical current densities, with no accompanying impact on the microstructure. Accurate grain size and shape determination within the Nb/sub 3/Sn layer is possible through SEM examination of fractured wire surfaces.
- Research Organization:
- Lawrence Berkeley Lab., CA (USA). Center for Advanced Materials
- DOE Contract Number:
- AC03-76SF00098
- OSTI ID:
- 5468784
- Report Number(s):
- LBL-21729; ON: DE86015201
- Country of Publication:
- United States
- Language:
- English
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Magnetic
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71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ALLOYS
CRITICAL CURRENT
CRITICAL FIELD
CRYSTAL STRUCTURE
CURRENTS
ELECTRIC CURRENTS
FABRICATION
GRAIN REFINEMENT
INTERMETALLIC COMPOUNDS
LAYERS
MAGNETIC FIELDS
MICROSTRUCTURE
NIOBIUM ALLOYS
NIOBIUM BASE ALLOYS
RELAXATION
STRESS RELAXATION
SUPERCONDUCTING WIRES
TIN ALLOYS
WIRES