Fluidity and microstructure formation during flow of Al- SiC particle composites |
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Authors: | F M Yarandi P K Rohatgi S Ray |
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Affiliation: | (1) American National Can Research Laboratory, 60010 Barrington, IL;(2) Department of Materials, University of Wisconsin—Milwaukee, P.O. Box 784, 53201 Milwaukee, WI |
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Abstract: | This article presents the results of casting and spiral fluidity in a Al-7 wt% Si alloy reinforced with 10,15, and 20 vol%
SiC particles in permanent molds. The fluidity of the Al-SiC slurry increases linearly with temperature up to about 760 °C.
Above this temperature, the casting fluidity of the Al-SiC particle slurry does not change significantly with an increase
in temperature. In several cases, the fluidity decreased at temperatures above 760 °C. The fluidity of Al-SiC melts containing
9-μm SiC particles decreased with an increase in volume percentage of SiC up to 15 vol% (the range studied), presumably due
to an increase in the viscosity of the melt with increasing volume percentage of dispersoid and changes in thermophysical
properties of the composite. However, the fluidity of Al-20 vol% SiC of 14-μm particle size is higher than the fluidity of
Al-15 vol% SiC 9-μm particles, indicating the role of particle size and surface area in de-creasing fluidity. Composite slurries
travel farther in a channel of larger cross sections compared to channels of smaller cross sections under similar conditions.
Casting fluidity increases linearly with an in-crease in cross section of the channel. A model has been proposed to calculate
the values of fluidity of the composite as a function of particle volume percent, superheat, flow velocity of the melt, and
the cross sec-tion of the flow channel. Experimental observations have been compared with the predictions of the model, and
some deviations have been attributed to settling and segregation of SiC particles observed through microstructural examination.
(on leave from Dept. of Metallurgy, University of Roorkee, Roorkee (U.P.)-247667, India) |
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Keywords: | aluminum fluidity metal matrix composites microstructure particles |
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