Modeling fluid flow in three-dimensional single crystal dendritic structures
Modeling fluid flow in three-dimensional single crystal dendritic structures
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DOI：
10.1016/j.actamat.2010.01.014
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发表时间：
2010-05
期刊：
影响因子：
9.4
通讯作者：
J. Madison;J. Spowart;D. Rowenhorst;L. Aagesen;K. Thornton;T. Pollock
中科院分区：
文献类型：
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作者：
J. Madison;J. Spowart;D. Rowenhorst;L. Aagesen;K. Thornton;T. Pollock
定向凝固过程中的对流会导致缺陷，如雀斑和取向不良的晶粒。为了更好地了解与对流不稳定性的发生相关的条件，在实验获得的树枝状网络中使用三维（3D）计算流体动力学模拟来研究流动。使用尺寸为2.3×2.3×1.5mm的定向凝固镍基高温合金的连续切片的3D数据集来确定作为固体分数（fS）的函数的平行于和垂直于凝固方向的流动的渗透率。渗透率的各向异性从0.4<fS<0.6显著变化。高流速通道表现出与糊状区底部的一次枝晶臂相当的间距，但朝向枝晶尖端迅速增加三到四倍。渗透性强烈依赖于界面表面积，其在fS=0.65时达到最大值。从3D模拟的结果也与经验渗透率模型进行了比较，并从这些模型偏离的微观结构的起源进行了讨论。
Convection during directional solidification can cause defects such as freckles and misoriented grains. To gain a better understanding of conditions associated with the onset of convective instabilities, flow was investigated using three-dimensional (3D) computational fluid dynamics simulations in an experimentally obtained dendritic network. A serial-sectioned, 3D data set of directionally solidified nickel-base superalloy measuring 2.3×2.3×1.5mm was used to determine the permeability for flow parallel and normal to the solidification direction as a function of solid fraction (fS). Anisotropy of permeability varies significantly from 0.4<fS<0.6. High flow velocity channels exhibit spacings commensurate with primary dendrite arms at the base of the mushy zone but rapidly increase by a factor of three to four towards dendrite tips. Permeability is strongly dependent on interfacial surface area, which reaches a maximum at fS=0.65. Results from the 3D simulation are also compared with empirical permeability models, and the microstructural origins of departures from these models are discussed.