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| SIMULATION OF EUTECTIC GROWTH IN DIRECTIONAL SOLIDIFICATION BY CELLULAR AUTOMATON METHOD |
| SHI Yufeng, XU Qingyan, LIU Baicheng |
| Key Laboratory for Advanced Materials Processing Technology, Ministry of Education, Department of Mechanical Engineering, Tsinghua University, Beijing 100084 |
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Cite this article:
SHI Yufeng XU Qingyan LIU Baicheng. SIMULATION OF EUTECTIC GROWTH IN DIRECTIONAL SOLIDIFICATION BY CELLULAR AUTOMATON METHOD. Acta Metall Sin, 2012, 48(1): 41-48.
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Abstract Eutectic microstructures are one of the most common solidification patterns in the binary or
multi-component alloy systems. Due to the fine periodic microstructures of the eutectic alloys, the commercial
applications of the eutectic alloys can improve the mechanical properties of the castings. The solidification
mechanism of eutectic alloys has been widely studied by a lot of experimental works and theoretical analysis over
the years. Recently, numerical models were used to study the mechanisms of formation of phase patterns and
selection dynamics of the lamellar eutectic, such as phase field (PF) and cellular automaton (CA) model, which
can promote the development of eutectic growth theory. Based on the existing CA method for
binary primary α phase, a modified cellular automaton (MCA) model was developed for the simulation of binary
eutectic growth. In this model, the influence of constitutional and curvature undercooling on the interface
morphology was considered. The growth rate of eutectic interface was calculated by the solute conservation at the
$\alpha$/liquid and $\beta$/liquid interfaces. The model could simulate the phenomenon of overgrowth, splitting and
steady state growth of the eutectic lamellar. CBr4-C2Cl6 eutectic transparent alloy was chosen to validate the model. The simulated results showed that the
increasing pulling rate lead to a smaller eutectic lamellar spacing, which had a
good agreement with the Jackson--Hunt theory and the experimental results from the literature. Eutectic
morphology evolution was simulated under a constant pulling rate and temperature gradient, which showed that
the stable lamellar structures existed when the initial lamellar spacing was in a finite range between the minimum
stable spacing λm and the limiting maximum stable spacing λm. A smaller initial lamellar
spacing would lead to lamellar annihilation. Conversely, a larger initial lamellar spacing could lead to the lamellar
nucleation due to the appearance of solute rich concave at the center of the α/liquid interface. Meanwhile,
the oscillatory instability of
the eutectic lamellar was also reappeared by the MCA model. The MCA model was easily extended to 3D, and
the lamellar-rod transition during directional solidification was simulated, which showed that the ratio of volume
fraction of α and β phase was smaller than 1/Π tend to form lamellar-rod transition
when the initial lamellar spacing was smaller than λm.
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Received: 18 July 2011
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| Fund: Supported by National Basic Research Program of China (Nos.2005CB724105 and 2011CB706801), National Natural Science Foundation of China (Nos.10477010 and 51171089), National High Technology Research and Development Program of China (No.2007AA04Z141) and Important National Science and Technology Specific Projects (Nos.2009ZX04006-041-04 and 2011ZX04014-052) |
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