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Lamellar Spacing Selection in Al-Si Eutectic System: a Theoretical InvestigationIt is well known that irregular eutectics such as Al-Si and Fe-C exhibit larger lamellar spacings and undercoolings compared to the predictions made by the Jackson and Hunt (JH) theory. In this paper, we reexamine the JH theory and relax some of the assumptions used in that treatment. The modified theoretical model has enhanced capabilities to predict the lamellar spacing in both regular and irregular eutectics. For the Al-Si system in particular we identified two different spacing selection mechanisms:a) for a particular growth rate, a nearly isothermal interface can be achieved at a unique minimum spacing lambda(sub I); b) the average spacing in the microstructure (lambda(sub av) greater than lambda(sub I)) is essentially dictated by the undercooling of the faceted phase. Based on the modified theoretical model a semi-empirical expression has been developed to account for the influence of the temperature gradient. Application of a Mullin and Sekerka type stability analysis for eutectics will also be presented and the results compared to the modified JH model. It will be shown that the both theoretical approaches are in good agreement with each other and also with the published experimental measurements.
Document ID
20010048750
Acquisition Source
Marshall Space Flight Center
Document Type
Conference Paper
Authors
Catalina, Adrian V.
(Universities Space Research Association Huntsville, AL United States)
Sen, Subhayu
(Universities Space Research Association Huntsville, AL United States)
Curreri, Peter A.
(NASA Marshall Space Flight Center Huntsville, AL United States)
Rose, M. Franklin
Date Acquired
August 20, 2013
Publication Date
January 1, 2001
Subject Category
Metals And Metallic Materials
Meeting Information
Meeting: Science of Casting and Solidifcation Conference
Location: Brasov
Country: Romania
Start Date: May 28, 2001
Funding Number(s)
CONTRACT_GRANT: NCC8-66
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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