Influence of crystallography upon critical nucleus shapes and kinetics of homogeneous f. c. c. -f. c. c. nucleation-IV. Comparisons between theory and experiment in Cu-Co alloys
A discrete lattice point model (Cook, de Fontaine and Hilliard) which incorporates strain energy (Cook and de Fontaine), described in earlier papers, has been used to determine the ranges of temperature and composition at which homogeneous nucleation kinetics of f.c.c. precipitates in Cu-Co alloys would be neither too fast nor too slow to be measured. These predictions proved successful and it was possible to measure experimentally nucleation kinetics in Cu-Co alloys containing from 0.5 to 1.0 at.% Co within 50/sup 0/C temperature ranges. Experimental results were compared with theoretical values obtained from the discrete lattice point, the Cahn-Hilliard continuum and the classical theories of homogeneous nucleation. Very good agreement was obtained between the experiments and all three theories. Although surprising at first, the good matching between classical theory and experiment was explained by showing that the calculated concentration profiles of critical nuclei at the temperatures and alloy compositions experimentally studied did show distinct ''volumes'' and ''interfaces'' i.e. the solute concentration did not vary continuously throughout the nuclei. In this case, as pointed out in effect by Cahn and Hilliard, classical nucleation theory indeed applies. These findings provide the first strong support for the essential correctness of homogeneous nucleation theory.
- Research Organization:
- Department of Metallurgical Engineering and Materials Science, Carnegie-Mellon University, Pittsburgh, PA
- OSTI ID:
- 6015182
- Journal Information:
- Acta Metall.; (United States), Journal Name: Acta Metall.; (United States) Vol. 32:10; ISSN AMETA
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
360102* -- Metals & Alloys-- Structure & Phase Studies
ALLOY SYSTEMS
ALLOYS
BINARY ALLOY SYSTEMS
CHEMICAL COMPOSITION
COBALT ALLOYS
COPPER ALLOYS
CRYSTAL LATTICES
CRYSTAL STRUCTURE
CRYSTALLOGRAPHY
CRYSTALS
CUBIC LATTICES
FCC LATTICES
KINETICS
MEASURING METHODS
MORPHOLOGY
NUCLEATION
PRECIPITATION
REACTION KINETICS
SEPARATION PROCESSES
STRAINS
TEMPERATURE GRADIENTS