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The influence of buoyant forces and volume fraction of particles on the particle pushing/entrapment transition during directional solidification of Al/SiC and Al/graphite compositesDirectional solidification experiments in a Bridgman-type furnace were used to study particle behavior at the liquid/solid interface in aluminum metal matrix composites. Graphite or silicon-carbide particles were first dispersed in aluminum-base alloys via a mechanically stirred vortex. Then, 100-mm-diameter and 120-mm-long samples were cast in steel dies and used for directional solidification. The processing variables controlled were the direction and velocity of solidification and the temperature gradient at the interface. The material variables monitored were the interface energy, the liquid/particle density difference, the particle/liquid thermal conductivity ratio, and the volume fraction of particles. These properties were changed by selecting combinations of particles (graphite or silicon carbide) and alloys (Al-Cu, Al-Mg, Al-Ni). A model which consideres process thermodynamics, process kinetics (including the role of buoyant forces), and thermophysical properties was developed. Based on solidification direction and velocity, and on materials properties, four types of behavior were predicted. Sessile drop experiments were also used to determine some of the interface energies required in calculation with the proposed model. Experimental results compared favorably with model predictions.
Document ID
19900035832
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
Authors
Stefanescu, Doru M.
(Alabama Univ. Tuscaloosa, AL, United States)
Moitra, Avijit
(Alabama Univ. Tuscaloosa, AL, United States)
Kacar, A. Sedat
(Alabama, University Tuscaloosa, United States)
Dhindaw, Brij K.
(Indian Institute of Technology Kharagpur, India)
Date Acquired
August 14, 2013
Publication Date
January 1, 1990
Publication Information
Publication: Metallurgical Transactions A - Physical Metallurgy and Materials Science
Volume: 21A
ISSN: 0360-2133
Subject Category
Composite Materials
Accession Number
90A22887
Funding Number(s)
CONTRACT_GRANT: NAGW-10
Distribution Limits
Public
Copyright
Other

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