论文标题
对流对柱状树突状固化的影响 - 多尺度树突针网络研究
Convective effects on columnar dendritic solidification -- A multiscale dendritic needle network study
论文作者
论文摘要
重力诱导的浮力，在大多数固化过程中不可避免地改变了晶体生长的动力学，因此将流体流入凝固模型中对于理解和预测微观结构选择的关键方面至关重要。在这里，我们提出了一个多尺度的树突针网络（DNN）模型，用于定向固化，其中包括液体中的浮力流，并将其应用于一系列合金和生长条件。在对该模型进行了简要介绍之后，我们研究了在不同重力水平下的Al-4AT。％Cu和Ti-45AT。％AL合金中稳定的原代树突臂间距的选择，将这两种应用与已发表的相位场结果和实验测量进行了比较。然后，我们模拟了最近通过X射线X射线对基于镍的Superaly CMSX-4定向固化的原位成像报道的振荡生长行为。在最后一次应用中，DNN模拟设法重现了振荡性生长行为，因此允许确定振荡性生长制度背后的基本机制。特别是，我们表明，当平均液态流速度接近晶体生长速度时，持续振荡就会发生，并且原发性树突间距在振荡行为中也起着至关重要的作用。
Gravity-induced buoyancy, inevitable in most solidification processes, substantially alters the dynamics of crystal growth, such that incorporating fluid flow in solidification models is crucial to understand and predict key aspects of microstructure selection. Here, we present a multi-scale Dendritic Needle Network (DNN) model for directional solidification that includes buoyant flow in the liquid, and apply it to a range of alloys and growth conditions. After a brief presentation of the model, we study the selection of stable primary dendrite arm spacings in Al-4at.%Cu and in Ti-45at.%Al alloys under different gravity levels, comparing both applications to published phase-field results and experimental measurements. Then, we simulate the oscillatory growth behavior recently reported via X-ray in situ imaging of directional solidification of nickel-based superalloy CMSX-4. In this last application, the DNN simulations manage to reproduce the oscillatory growth behavior, and hence permit identifying the fundamental mechanisms behind the oscillatory growth regime. In particular, we show that sustained oscillations occur when the average liquid flow velocity is close to the crystal growth velocity, and that primary dendritic spacings also play a crucial role in the oscillatory behavior.
