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Effects of Gravity on the Double-Diffusive Convection During Directional Solidification of a Non-Dilute Alloy with Application to HgCdTeA general 2-D and 3-D finite element model of non-dilute alloy solidification was used to simulate growth of HgCdTe in terrestrial and microgravity conditions. Verification of the 3-D model was undertaken by comparison with previously published results on convection in an inclined cylinder. For low growth velocities, plane front solidification occurs. The location and the shape of the interface were determined using melting temperatures obtained from the HgCdTe liquidus curve. The low thermal conductivity of the solid HgCdTe causes a thermal short circuit through the ampoule walls, resulting in curved isotherms in the vicinity of the interface. Double-diffusive convection in the melt is caused by radial temperature gradients and by material density inversion due to the combined effects of composition and temperature. Cooling from below and the rejection at the solid-melt interface of the heavier HgTe-rich solute each tend to reduce convection. Because of these complicating factors, dimensional rather than non-dimensional modeling was performed. the predicted interface shape is in agreement with one obtained experimentally by quenching.
Document ID
19990094261
Acquisition Source
Marshall Space Flight Center
Document Type
Preprint (Draft being sent to journal)
Authors
Bune, Andris V.
(Alliance for Microgravity Materials Science and Applications Huntsville, AL United States)
Gillies, Donald C.
(NASA Marshall Space Flight Center Huntsville, AL United States)
Lehoczky, Sandor L.
(NASA Marshall Space Flight Center Huntsville, AL United States)
Date Acquired
August 19, 2013
Publication Date
January 1, 1999
Subject Category
Materials Processing
Funding Number(s)
CONTRACT_GRANT: NCC8-66
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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