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Quantitative micro-modeling of dendrite growth controlled by solutal effects in the low Peclet regime for binary alloys.

机译：二元合金在低Peclet态中受溶蚀作用控制的枝晶生长的定量微观模型。

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摘要

While a number of cellular automaton (CA) based models for dendrite growth were proposed none so far have been validated, casting doubt on their quantitative capabilities. Furthermore, these models are mesh-dependent and cannot correctly describe crystallographic orientation. In this work, a CA-based model is proposed for dendrite growth controlled by solutal effects in the low solutal Peclet number regime. The model does not use an analytical solution to determine the velocity of the solid-liquid interface as function of undercooling common in other models. Instead, it solves the solute and heat conservation equations subjected to the boundary conditions at the interface. Using this approach the model does not need to use the concept of marginal stability and stability constant to uniquely define the steady state velocity and radius of the dendrite tip. The model contains an expression for the stability parameter but the process determines its value. It is found that the stability parameter is not a constant, but rather changes with time and angular position during dendrite formation. The model proposes solutions for the evaluation of local curvature, solid fraction, trapping rules and anisotropy of the mesh, which eliminates the mesh dependency of calculations, common in other models. The model is able to reproduce most of the dendritic features observed experimentally, such as secondary and tertiary branching, parabolic tip, arms generation and selection, etc. Computation results are validated in three ways. First, the simulated secondary dendrite arm spacing is compared with literature values for an Al-4wt% Cu alloy. Second, the predictions of the classic Lipton-Glicksman-Kurz theory for steady state tip velocity and radius, are compared with simulated values as function of melt undercooling for Al-4wt%Cu and Fe-0.6wt%C alloys. Finally, simulated results for succinotrile-0.29wt% acetone model alloy are compared with experimental data. Model calculations were found to be in very good agreement with both the analytical model and the experimental data. The CA model is used to simulate equiaxed and columnar growth offering insight into microstructure formation under these conditions.
机译：尽管目前尚未提出许多基于细胞自动机（CA）的枝晶生长模型的验证，但对它们的定量能力提出了疑问。此外，这些模型与网格有关，无法正确描述晶体学取向。在这项工作中，提出了一种基于CA的模型，用于在低稀溶液Peclet数体制下通过稀溶液效应控制枝晶生长。该模型未使用解析解决方案来确定固-液界面的速度作为其他模型中常见的过冷函数。取而代之的是，它求解界面处边界条件下的溶质守恒方程和热守恒方程。使用这种方法，模型不需要使用边际稳定性和稳定性常数的概念来唯一地定义稳态速度和枝晶尖端的半径。该模型包含稳定性参数的表达式，但过程将确定其值。发现稳定性参数不是常数，而是在枝晶形成过程中随时间和角位置而变化。该模型提出了用于评估局部曲率，实心分数，捕获规则和网格各向异性的解决方案，从而消除了其他模型中常见的网格依赖计算。该模型能够重现通过实验观察到的大多数树枝状特征，例如二级和三级分支，抛物线形尖端，臂的生成和选择等。计算结果可通过三种方式进行验证。首先，将模拟的二次枝晶臂间距与Al-4wt％Cu合金的文献值进行比较。其次，将经典Lipton-Glicksman-Kurz理论对稳态尖端速度和半径的预测与模拟值（对于Al-4wt％Cu和Fe-0.6wt％C合金的熔体过冷函数进行比较）进行了比较。最后，将丁二腈-0.29wt％丙酮模型合金的模拟结果与实验数据进行了比较。发现模型计算与分析模型和实验数据都非常吻合。 CA模型用于模拟等轴和柱状生长，从而洞察在这些条件下的微观结构。

著录项

  • 作者

    Beltran-Sanchez, Lazaro.;

  • 作者单位

    The University of Alabama.;

  • 授予单位 The University of Alabama.;
  • 学科 Engineering Metallurgy.; Engineering Materials Science.
  • 学位 Ph.D.
  • 年度 2003
  • 页码 147 p.
  • 总页数 147
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 冶金工业;工程材料学;
  • 关键词

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