Front Tracking Based Macroscopic Calculations of Columnar and Equiaxed Solidification of a Binary Alloy
Front Tracking Based Macroscopic Calculations of Columnar and Equiaxed Solidification of a Binary Alloy
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基于前沿跟踪的二元合金柱状和等轴凝固宏观计算
DOI：
10.1115/1.4001362
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发表时间：
2010
影响因子：
--
通讯作者：
J. Banaszek
中科院分区：
文献类型：
--
作者：
M. Seredyński;J. Banaszek
本文探讨了最近发展的一种特殊的前沿跟踪方法在确定二元合金在热溶解对流驱动下的凝固过程中形成的柱状组织和等轴组织之间的界面的潜力。该方法基于理论和实验的枝晶尖端动力学，能够直接区分柱状混浊和在枝晶尖端曲线之前发展的过冷液化区。提出了一种新的数值模型及其计算算法，其中输运过程的经典欧拉体积平均描述与拉格朗日锋面跟踪方法在固定的控制体积网格上相结合。因此，具有不同枝晶结构的不同区域，在每个区域内使用不同的模拟模型，例如，静止枝晶区域中的达西多孔介质模型，以及在糊料的等轴部分中具有浮动枝晶的泥浆模型。以扩散和热溶质对流驱动的铅-48wt%锡合金凝固问题为例，将计算的温度场和溶质浓度场与经典的热焓-孔隙率模型的相关结果进行了比较。与这两种解决方案都有很好的匹配性。通过将现有的实验数据与模型预测进行比较，也给出了初步的验证研究。讨论了观测到的计算结果与实验结果之间存在差异的可能原因。最后，利用提出的前沿跟踪方法研究了液态中漂浮的树枝晶对合金凝固过程中流动形态和宏观偏析的影响。
The paper explores the potential of a recently developed special front tracking method in the identification of the interface between columnar and equiaxed structures formed during a binary alloy solidification, driven by thermosolutal convection. The method, based on theoretical and experimental dendrite tip kinetics, is capable of directly distinguishing between the columnar mush and the undercooled liquidlequiaxed region developing ahead of the dendrite tip curve. A new numerical model and its computational algorithm are proposed, where the classical Eulerian volume averaged description of the transport processes is coupled with the Lagrangian front tracking method on a fixed control-volume grid. Having thus distinguished zones of different dendrite structures, distinct simulation models are used within each of the zones, e.g., the Darcy's porous medium model in the stationary dendrite region, and a model of slurry with floating dendrites in the equiaxed part of the mush. The calculated temperature and solute concentration fields are compared with the relevant results of the classical enthalpy-porosity model, for an example problem of Pb-48 wt % Sn alloy solidification driven by diffusion and thermosolutal convection. And a good match with both solutions is exhibited. A preliminary validation study is also presented by comparing the available experimental data with the model predictions. Possible reasons for some observed discrepancies between the calculations and the experimental findings are discussed. Finally, the proposed front tracking approach is used to address the question of the impact of dendrites floating in the liquid on the flow pattern and macrosegregation in the solidifying alloy.