Microstructural evolution and growth velocity-undercooling relationships in the systems Cu, Cu-O and Cu-Sn at high undercooling

A melt encasement (fluxing) technique has been used to systematically study the velocity-undercooling relationship in samples of Cu and Cu-O and Cu-3 wt% Sn at undercoolings up to 250 K. In pure Cu the solidification velocity increased smoothly with undercooling up to a maximum of 97 m s-1. No evide...

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Bibliographic Details
Published in:Journal of materials science 2000-01, Vol.35 (6), p.1365-1373
Main Authors: BATTERSBY, S. E, COCHRANE, R. F, MULLIS, A. M
Format: Article
Language:English
Subjects:
Applied sciences
Copper
Cross-disciplinary physics: materials science
rheology
Exact sciences and technology
Fluxing
Grain refinement
Materials science
Melts
Metals. Metallurgy
Microhardness
Microstructural analysis
Microstructure
Phase diagrams and microstructures developed by solidification and solid-solid phase transformations
Physics
Recrystallization
Solidification
Substructures
Supercooling
Tin
Velocity
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Summary:A melt encasement (fluxing) technique has been used to systematically study the velocity-undercooling relationship in samples of Cu and Cu-O and Cu-3 wt% Sn at undercoolings up to 250 K. In pure Cu the solidification velocity increased smoothly with undercooling up to a maximum of 97 m s-1. No evidence of grain refinement was found in any of the as-solidified samples. However, in Cu doped with >200 ppm O we found that samples undercooled by more than 190 K had a grain refined microstructure and that this corresponded with a clear discontinuity in the velocity-undercooling curve. Microstructural evidence in these samples is indicative of dendritic fragmentation having occurred. In Cu-Sn grain refinement was observed at the highest undercoolings (greater than 190 K in Cu-3 wt% Sn) but without the spherical substructure seen to accompany grain refinement in Cu-O alloys. Microstructural analysis using light microscopy, texture analysis and microhardness measurements reveals that recrystallisation accompanies the grain refinement at high undercoolings. Furthermore, at undercoolings between 110 K and 190 K, a high density of subgrains are seen within the microstructure which indicate the occurrence of recovery, a phenomenon previously unreported in samples solidified from highly undercooled melts.
ISSN:0022-2461
1573-4803
DOI:10.1023/A:1004782107849