X-ray radiography observations of columnar dendritic growth and constitutional undercooling in an Al–30wt%Cu alloy

In situ synchrotron X-ray radiography of columnar dendritic and eutectic growth under directional solidification of Al–30wt%Cu has been carried out with nominal spatial and temporal resolutions of 1.4 μm and 150 ms, respectively. The images can be processed to reveal spatiotemporal co-ordinates of t...

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Bibliographic Details
Published in:Acta materialia 2005-02, Vol.53 (4), p.947-956
Main Authors: Mathiesen, Ragnvald H., Arnberg, Lars
Format: Article
Language:English
Subjects:
ALUMINIUM ALLOYS
BOUNDARY LAYERS
Constitutional undercooling
COPPER ALLOYS
DENDRITES
Dendritic growth
Directional solidification
EUTECTICS
MATERIALS SCIENCE
MICROSTRUCTURE
SOLIDIFICATION
SUBCOOLING
SYNCHROTRON RADIATION
X-RAY RADIOGRAPHY
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Summary:In situ synchrotron X-ray radiography of columnar dendritic and eutectic growth under directional solidification of Al–30wt%Cu has been carried out with nominal spatial and temporal resolutions of 1.4 μm and 150 ms, respectively. The images can be processed to reveal spatiotemporal co-ordinates of the solid–liquid phase fronts for both α-dendrites and the proceeding eutectic. Also estimates for local solute boundary layers ahead of and in the mushy zone can be extracted from image processing. Steady-state growth could not be realized in the experiments. Presumably this relates to a combination of: (a) insufficient time available for initial instabilities to evolve into a steady state; (b) primary α-branches may interact through solute diffusion in the confined sample volume; (c) the inevitable presence of thermo-solutal flow; and (d) a long-term sample position dependent drift in the furnace to sample heat transfers. Nevertheless, the data collected contain information that may be valuable for microstructure modelling of dendritic growth.
ISSN:1359-6454
1873-2453
DOI:10.1016/j.actamat.2004.10.050