A Rayleigh number based dendrite fragmentation criterion for detachment of solid crystals during solidification

Kumar, Arvind and Dutta, Pradip (2008) A Rayleigh number based dendrite fragmentation criterion for detachment of solid crystals during solidification. In: Journal of Physics D-Applied Physics, 41 (15). p. 155501.

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Abstract

Movement of solid crystals in the form of dendrite fragments causes severe macro-segregation in solidified products. Dendrite fragmentation in the developing mushy zone occurs as a result of remelting (causing dissolution) and subsequent breakage of dendritic side arms from the dendritic stalks. An understanding of the mechanisms of dendrite fragmentation is essential for predicting the transport of fragmented solid crystals for possible control of macro-segregation. In this work, a Rayleigh number based fragmentation criterion is developed for detachment of dendrites from the developing mushy zone, which determines the conditions favourable for fragmentation of dendrites. The Rayleigh number, defined in this paper, measures the ratio of the driving buoyancy force for the flow in the mushy zone to the retarding frictional force associated with the permeability of the mush. The criterion developed is a function of the concentration difference, liquid fraction, permeability, growth rate of mushy layer and thermophysical properties of the material

Item Type:	Journal Article
Publication:	Journal of Physics D-Applied Physics
Publisher:	Institute of Physics Publishing Ltd
Additional Information:	Copyright of this article belongs to Institute of Physics Publishing Ltd.
Department/Centre:	Division of Mechanical Sciences > Mechanical Engineering
Date Deposited:	06 Oct 2008 10:52
Last Modified:	19 Sep 2010 04:51
URI:	http://eprints.iisc.ac.in/id/eprint/16151

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