Abstract The eutectic structure has significant effects on the mechanical properties of Al-Si alloys. However, predicting the formation and morphology of the eutectic structure is difficult, especially under a large range of undercooling. In this paper, a comprehensive model taking account of the eutectic point migration and a dynamic concentration nucleation criterion was developed based on a cellular automaton method to predict the irregular eutectic structure of Al-Si alloys, and the evolution mechanism of the Al-Si irregular eutectic under a large range of undercooling of 5–20 K was numerically investigated. This model was then applied to predict the hypoeutectic microstructures of two processes with greatly different cooling rates: a traditional casting process (copper mold casting) and an additive manufacturing process (selective laser melting), in which the cooling and solidification characteristics of AlSi10Mg alloys were calculated by a double-solid-liquid interface enthalpy model. The results indicate that the eutectic Al and Si present a synergistic effect to promote the crystallization rate significantly, the solidification rate of eutectic is much higher than that of primary, and the morphology of eutectic Si changes from coarse lamellar structure to refined particles as the increase of the eutectic undercooling.

中文翻译：

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大过冷度下Al-Si合金不规则共晶的数值研究

摘要 共晶组织对Al-Si合金的力学性能有显着影响。然而，预测共晶组织的形成和形态是困难的，尤其是在大范围过冷度下。在本文中，基于元胞自动机方法开发了一个考虑共晶点迁移和动态浓度成核准则的综合模型来预测铝硅合金的不规则共晶结构，以及铝硅不规则的演化机制。对大范围过冷度 5-20 K 下的共晶进行了数值研究。然后应用该模型来预测冷却速率差异很大的两种工艺的亚共晶微观结构：传统铸造工艺（铜模铸造）和增材制造工艺（选择性激光熔化），其中 AlSi10Mg 合金的冷却和凝固特性通过双固液界面焓模型计算。结果表明，共晶Al和Si呈现协同效应，显着促进结晶速率，共晶凝固速率远高于初晶凝固速率，共晶Si的形貌随着增加而由粗大片状结构转变为细化颗粒。共晶过冷度。