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Response of Mnbi-Bi Eutectic to Freezing Rate Changes

Published online by Cambridge University Press:  15 February 2011

M. Nair ,
T-W. Fu ,
W. R. Wilcox ,
K. Doddi ,
P. S. Ravishankar  and
D. Larson
M. Nair
Affiliation:
Department of Chemical Engineering, Clarkson College of Technology, Potsdam, New York 13676, USA
T-W. Fu
Affiliation:
Department of Chemical Engineering, Clarkson College of Technology, Potsdam, New York 13676, USA
W. R. Wilcox
Affiliation:
Department of Chemical Engineering, Clarkson College of Technology, Potsdam, New York 13676, USA
K. Doddi
Affiliation:
Department of Chemical Engineering, Clarkson College of Technology, Potsdam, New York 13676, USA
P. S. Ravishankar
Affiliation:
Department of Chemical Engineering, Clarkson College of Technology, Potsdam, New York 13676, USA
D. Larson
Affiliation:
Grumman Aerospace Corporation, Bethpage, New York 11714, USA
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Abstract

Previously we reported on a theoretical treatment of the influence on freezing rate of sudden changes in translation rate in the Bridgman-Stockbarger technique [11]. This has now been extended to consideration of a linear ramped translation rate and an oscillatory freezing rate. Oscillations above a few hertz are found to be highly damped in smalldiameter apparatus.

An experimental test was made of the theoretical predictions for a sudden change of translation rate. MnBi-Bi eutectic was solidified with current induced interface demarcation.The experimental results correspond reasonably well with theory if the silica ampoule wall is assumed either (1) to contribute only a resistance to heat exchange of sample with the furnace wall, or (2) to transmit heat effectively in the axial direction by radiation.

In an attempt to explain the fact that a finer microstructure is obtained in space, MnBi-Bi microstructure is being determined when the freezing rate is rapidly increased or decreased. Preliminary results indicate that fiber branching does not occur as readily as does fiber termination.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 9 , 1981 , 533
Copyright
Copyright © Materials Research Society 1982

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Footnotes

*

Present address: EPA, State Government of Delaware, Dover, Delaware 19901

**

Present address: Exxon R&D, Linden, New Jersey.

References

REFERENCES

1.Fu, T-W. and Wilcox, W. R., J. Crystal Growth 51, 557 (1981).Google Scholar
2.Fu, T-W. and Wilcox, W. R., “Programmed and Oscillatory Motion in Bridgman- Stockbarger Growth,” submitted to J. Crystal Growth.Google Scholar
3.Fu, T-W., Ph.D. Thesis, “Heat Transfer in the Bridgman-Stockbarger Technique,” 1981.Google Scholar
4.Fu, T-W., Wilcox, W. R. and Larson, D. J., “Rate Change Transients in Bridgman- Stockbarger Growth of MnBi-Bi Eutectic,” submitted to J. Crystal Growth.Google Scholar
5.Nair, M., Thesis, M.S., “Effect of Changes in Growth Velocity on the Microstructure of MnBi-Bi Eutectic,” 1981.Google Scholar
6.Doddi, K., Thesis, M.S., “Influence of Freezing Rate Changes on Microstructure of MnBi/Bi Eutectic,” in progress.Google Scholar