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Containerless Processing of Undercooled Melts

Published online by Cambridge University Press:  26 February 2011

D. S. Shong
Affiliation:
Department of Metallurgical and Mineral Engineering, University of Wisconsin-Madison, Madison, WI 53706
J. A. Graves
Affiliation:
Department of Metallurgical and Mineral Engineering, University of Wisconsin-Madison, Madison, WI 53706
Y. Ujiie
Affiliation:
Department of Metallurgical and Mineral Engineering, University of Wisconsin-Madison, Madison, WI 53706
J. H. Perepezko
Affiliation:
Department of Metallurgical and Mineral Engineering, University of Wisconsin-Madison, Madison, WI 53706
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Abstract

Containerless drop tube processing allows for significant levels of liquid undercooling through control of parameters such as sample size, surface coating and cooling rate. A laboratory scale (3m) drop tube has been developed which allows the under-cooling and solidification behavior of powder samples to be eval-uated under low gravity free fall conditions. The level of undercooling obtained in an InSb-Sb eutectic alloy has been eval-uated by comparing the eutectic spacing in drop tube samples with a spacing/undercooling relationship established using thermal analysis techniques. Undercoolings of 0.17 and 0.23 Te were produced by processing under vacuum and He gas conditions respec-tively. Alternatively, the formation of an amorphous phase in a Ni-Nb eutectic alloy indicates that undercooling levels of approximately 500°C were obtained by drop tube processing. The influence of droplet size and gas environment on undercooling behavior in the Ni-Nb eutectic was evaluated through their effect on the amorphous/crystalline phase ratio. To supplement the structural analysis, heat flow modeling has been developed to describe the undercooling history during drop tube processing and the model has been tested experimentally.

Type
Research Article
Copyright
Copyright © Materials Research Society 1987

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