ISSN: 1546-962X
CODEN: JAIOAD
Published Online: 20 October 2011
Page Count: 10

Effect of Chemical Modification of Al-Si Alloys on Thermal Diffusivity and Contact Heat Transfer at the Casting–Chill Interface

Prabhu, K. Narayan
Dept. of Metallurgical & Materials Engineering, National Institute of Technology Karnataka,

, Jayananda


Hegde, Sathyapal
Dept. of Metallurgical & Materials Engineering, National Institute of Technology Karnataka,

(Received 27 May 2011; accepted 26 September 2011)

Abstract

The heat flow during the unidirectional downward solidification of Al-7Si and Al-12Si alloys was analyzed using thermal analysis technique and inverse modeling. Chills instrumented with thermocouples were brought into contact with a small pool of liquid metal so as to minimize the effect of convection caused by pouring and temperature gradients. Modification melt treatment resulted in an increase in the cooling rate of the solidifying casting near the casting–chill interfacial region. The corresponding interfacial heat flux transients were also found to be higher. The thermal diffusivities of alloys were measured using a laser pulse technique and were found to be higher for modified alloys. However, the increase in the heat flux transients was attributed mainly to the improvement in the casting–chill interfacial thermal contact condition brought about by the decrease in the surface tension of the liquid metal upon the addition of sodium.

Keywords:
chills, solidification, modification, diffusivity

Paper ID: JAI104057
DOI: 10.1520/JAI104057
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