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Rheological Behavior of Semi-solid Slurry of A356 Alloy at High Shear and Cooling Rates

Barman, N and Dutta, P (2008) Rheological Behavior of Semi-solid Slurry of A356 Alloy at High Shear and Cooling Rates. In: 10th International Conference on Semi-Solid Processing of Alloys and Composites, September 16th -18th, 2008., Aachen, Germany, pp. 409-414.

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Abstract

The rheological behavior of semisolid aluminium alloy (A356) slurry is investigated by using a concentric cylinder viscometer under high cooling rate (30 to 50 degrees C/min) and high shear rate (650 to 1500s(-1)) conditions. Two different series of experiments are carried out. In all of these experiments, the pellets of A356 alloy are poured into the outer cylinder where they melt completely by resistance heating. When the inner cylinder is placed concentrically, the molten metal resides in the annular space between the cylinders. As the inner cylinder rotates, the alloy is sheared continuously during cooling from a temperature of 630 degrees C, and a slurry forms. In the first series of experiments, for different cooling rates, shearing continues under a constant shear rate until rotation of the inner cylinder stops. During experiments, the temperature of the slurry is measured continuously using a K-type thermocouple, from which the solid fraction is calculated. In the second series of experiments, the molten alloy is cooled and sheared continuously at different shear rates for a given cooling rate. The apparent viscosity of the slurry is calculated by measuring the torque applied to the inner cylinder and its rotational speed. The results show that the slurry viscosity increases with increasing fraction of solid and increasing cooling rate, and it decreases with increasing shear rate. At high values of shear and cooling rates, the viscosity varies gradually up to a solid fraction of about 0.5.

Item Type: Conference Paper
Additional Information: Copyright of this article belongs to Trans Tech Publications Inc.
Keywords: Semisolid slurry;apparent viscosity;solid fraction;shear rate;cooling rate.
Department/Centre: Division of Mechanical Sciences > Mechanical Engineering
Date Deposited: 05 Nov 2009 06:53
Last Modified: 05 Nov 2009 06:53
URI: http://eprints.iisc.ernet.in/id/eprint/18824

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