Microstructural investigation of the bcc to A15 phase transition in sputter-deposited Nb/sub 3/Al superconductors
The bcc to A15 phase transition in sputter-deposited Nb/sub 3/Al (Cb/sub 3/Al) superconductors was studied using transmission electron microscopy. Four distinct microstructures were observed for the sputter-deposited and isochronally heat treated samples. Heat treatments were for 24 h at temperatures between 500 and 700/sup 0/C. Deposition at 10/sup 0/C produced the bcc phase with a small grain size of 1000A. The bcc grains contained a high density of dislocations and fine precipitates. Coarse precipitates were found in the bcc grains and at the grain boundaries after heat treatment between 500 and 600/sup 0/C. At 650/sup 0/C, the A15 phase was detected in the presence of the bcc phase; the nucleation of the A15 phase originated at the grain boundary. Finally, a homogeneous microstructure of A15 phase resulted from heat treatment at 700/sup 0/C. The A15 phase had a small, but defect free grain of 2500A. It is believed that such microstructures of A15 phase could have enhanced superconducting critical current (J/sub c/) and critical temperature (T/sub c/).
- Research Organization:
- Battelle Pacific Northwest Labs., Richland, WA
- OSTI ID:
- 6517952
- Journal Information:
- Metall. Trans., A; (United States), Journal Name: Metall. Trans., A; (United States) Vol. 8:11; ISSN MTTAB
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
360101* -- Metals & Alloys-- Preparation & Fabrication
360102 -- Metals & Alloys-- Structure & Phase Studies
656102 -- Solid State Physics-- Superconductivity-- Acoustic
Electronic
Magnetic
Optical
& Thermal Phenomena-- (-1987)
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ALLOYS
ALUMINIUM ALLOYS
COATINGS
COPPER
CRYSTAL STRUCTURE
ELECTRIC CONDUCTIVITY
ELECTRICAL PROPERTIES
ELECTRON MICROSCOPY
ELEMENTS
GRAIN BOUNDARIES
GRAIN SIZE
HEAT TREATMENTS
HYDROGEN COMPOUNDS
INORGANIC ACIDS
METALS
MICROSCOPY
MICROSTRUCTURE
NIOBIUM ALLOYS
NIOBIUM BASE ALLOYS
NITRIC ACID
NUCLEATION
ORIENTATION
PHYSICAL PROPERTIES
PRECIPITATION
SEPARATION PROCESSES
SIZE
SPUTTERING
SUPERCONDUCTIVITY
SUPERCONDUCTORS
TRANSITION ELEMENTS
TRANSMISSION ELECTRON MICROSCOPY
VAPOR DEPOSITED COATINGS