A new analytical approach to predict spacing selection in lamellar and rod eutectic systems |
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Authors: | Adrian V Catalina Subhayu Sen Doru M Stefanescu |
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Affiliation: | (1) USRA/SD46, NASA Marshall Space Flight Center, 35812 Huntsville, AL;(2) the Solidification Laboratory, The University of Alabama, 35487 Tuscaloosa, AL |
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Abstract: | The Jackson and Hunt (JH) theory has been modified to relax the assumption of isothermal solid/liquid interface used in their
treatment. Based on the predictions of this modified theory, the traditional definitions of regular and irregular eutectics
are revised. For regular eutectics, the new model identifies a range of spacing within the limits defined by the minimum undercooling
of the α and β phases. For the irregular Al-Si eutectic system, two different spacing selection mechanisms were identified: (1) for a particular
growth rate, a nearly isothermal interface can be achieved at a unique minimum spacing λ
I
; (2) the average spacing (λ
av
>λ
I
) is essentially dictated by the undercooling of the faceted phase. Based on the modified theoretical model, a semiempirical
expression has been developed to account for the influence of the temperature gradient, which is dominant in the irregular
Al-Si system. The behavior of the Fe-Fe3C eutectic is also discussed. The theoretical calculations have been found to be in good agreement with the published experimental
measurements. |
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Keywords: | |
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