采用改进的元胞自动机方法对三元Al-Si-Mg合金凝固微观组织进行数值模拟

Numerical simulation of solidified microstructure of ternary Al-Si-Mg alloy using an improved cellular automaton method

铝硅合金具有轻量化、高强度和易成形等独特优点.这些特性使得在低压压铸下能够生产大型、薄壁、复杂的铸件,这对于车辆轻量化至关重要.然而,这些合金的铸造过程容易产生缺陷,它们的性能与微观结构密切相关.认识到工艺、结构和性能之间的深层联系具有巨大的学术和工程价值.在本工作中,我们通过整合热力学、动力学和多元相图数据库,建立了一个改进的元胞自动机(ICA)模型.基于在阶梯铸件不同位置的冷却曲线和凝固组织,我们建立了适用于Al-7SixMg合金低压铸造的等轴晶形核模型.随后对该合金进行了低压铸造实验,微观结构演变的3D模拟结果与实验观察相吻合.我们进行了阶梯件低压铸造的实验,ICA模型准确地描绘了α-Al树枝晶,以及冷却速率对三元Al-7Si-xMg合金中晶核密度和树枝晶尺寸均匀性的影响.我们的模拟结果与实验数据表现出显著的一致性.此外,我们对SDAS与冷却速率之间的关系进行了全面分析.通过将ICA模型与LGK分析模型进行对比,验证了在评估树枝晶生长速率时ICA模型的精确性.这项工作为集成计算材料工程建立凝固-组织-性能的定量关系提供了理论指导.

Al-Si alloys offer distinctive advantages including light weight,high strength,and excellent formability.These attributes enable the production of large,thin-walled complex castings under low-pressure die casting,which is pivotal for vehicle lightweighting.However,the casting process of these alloys is susceptible to defects,and their performance is intricately linked to their microstructure.Recognizing the deep-seated connection between process,structure,and performance is of immense academic and engineering value.In this work,by integrating the thermodynamics,kinetics,and multi-component phase diagram database,we formulated an improved cellular automata(ICA)model.Relying on cooling curves and solidification microstructures at varied positions of the step casting,we established an equiaxed crystal nucleation model apt for the low-pressure casting of the Al-7Si-xMg alloy.Subsequent three-dimensional simulations of the microstructural evolution during this alloy's low-pressure casting solidification mirrored experimental observations,particularly concerning dendrite morphology.Experiments on lowpressure casting of step-shaped components were conducted.The ICA model accurately depicted a-Al dendrites and the cooling rate's impact on nucleation density and dendrite size uniformity in the ternary Al-7Si-xMg alloy.Our simulation results demonstrated a remarkable consistency with experimental data.Further,we provided a comprehensive analysis of the relationship between secondary dendrite arm spacing and cooling rate.The precision of the ICA model,when assessing dendrite tip growth rate,was corroborated by juxtaposing it with the Lipton-Glicksman-Kurz(LGK)analytical model.This work provides theoretical guidance for the establishment of a quantitative relationship of solidification-microstructureproperties within the framework of integrated computational materials engineering.