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Modeling of aluminum-silicon irregular eutectic growth by cellular automaton model

China Foundry 2016年第2期13卷 114-122页

作者： Rui Chen Qing-yan Xu Bai-cheng Liu School of Materials Science and Engineering Tsinghua University Key Laboratory of Advanced Materials Processing Technology MOE

Due to the extensive application of Al-Si alloys in the automotive and aerospace industries as structural components, an understanding of their microstructural formation, such as dendrite and(Al+Si) eutectic, is of great importance to control the desirable microstructure, so as to modify the performance of castings. Since previous major themes of microstructural simulation are dendrite and regular eutectic growth, few efforts have been paid to simulate the irregular eutectic growth. Therefore, a multiphase cellular automaton(CA) model is developed and applied to simulate the time-dependent Al-Si irregular eutectic growth. Prior to model establishment, related experiments were carried out to investigate the influence of cooling rate and Sr modification on the growth of eutectic Si. This CA model incorporates several aspects, including growth algorithms and nucleation criterion, to achieve the competitive and cooperative growth mechanism for nonfaceted-faceted Al-Si irregular eutectic. The growth kinetics considers thermal undercooling, constitutional undercooling, and curvature undercooling, as well as the anisotropic characteristic of eutectic Si growth. The capturing rule takes into account the effects of modification on the silicon growth *** simulated results indicate that for unmodified alloy, the higher eutectic undercooling results in the higher eutectic growth velocity, and a more refined eutectic microstructure as well as narrower eutectic lamellar spacing. For modified alloy, the eutectic silicon tends to be obvious fibrous morphology and the morphology of eutectic Si is determined by both chemical modifier and cooling rate. The predicted microstructure of Al-7Si alloy under different solidification conditions shows that this proposed model can successfully reproduce both dendrite and eutectic microstructures.

关键词： Al-Si alloys irregular eutectic growth cellular automaton modification numerical simulation

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Rapid solidification of Ag-Si eutectic alloys in drop tube

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Progress in Natural Science:Materials International 1999年第9期 48-56页

作者：曹崇德,王楠,魏炳波,GROH Henry C Laboratory of Materials Science in Space Department of Applied Physics Northwestern Polytechnical University Xi'an 710072 China Laboratory of Materials Science in Space Department of Applied Physics Northwestern Polytechnical University Xi'an 710072 China Laboratory of Materials Science in Space Department of Applied Physics Northwestern Polytechnical University Xi'an 710072 China NASA Lewis Research Center Cleveland OH 44135 USA

Rapid solidification has been investigated on Ag-2.5%Si hypoeutectic, Ag-3 .1 % Si eutectic, and Ag-5 % Si (weight percentage) hypereutectic alloys in a 3-m drop tube. The irregular eutectic microstructures vary with droplet size and composition. Grain refinement has occurred to primary Ag dendrites, and to primary and eutectic Si with the decrease of droplet diameter. The interphase spacing was measured experimentally and calculated theoretically based on the modified Jackson-Hunt and Trivedi-Magnin-Kurz eutectic growth models. The growth velocity was also predicted by these two models. The operating range parameter Φ has been obtained approximately to be 2.614. It is presumed that Marangont convection may be responsible for the central distribution of primary Si blocks in the hypereutectic alloy. Appearance of primary Ag phase in the euiectic alloy and a novel microstructure characterized by primary Ag grains with a few Si blocks distributing in the fine globular eutectic matrix in small droplets of

关键词： rapid solidification Ag-Si irregular eutectic growth drop tube.

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