Pseudo-4D view of the growth and form of locked eutectic colonies
Pseudo-4D view of the growth and form of locked eutectic colonies
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DOI：
10.1016/j.actamat.2022.118335
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发表时间：
2022-09-18
期刊：
影响因子：
9.4
通讯作者：
Shahani, Ashwin J.
中科院分区：
文献类型：
--
作者：
Chao, Paul;Lindemann, George R.;Shahani, Ashwin J.
我们研究 Al-Cu 合金的凝固作为模型系统，以了解共晶团内图案（如层状、棒状和迷宫状）的出现。为了揭示原位和 3D 形态转变，我们在此引入一种新的基于同步加速器的程序，称为伪 4D X 射线成像。与传统成像方法相比，我们的方法同时最大化了时间（200 ms）和空间分辨率（0.69 2 mu m2/像素）。从这个过程中获得的大量信息使我们能够在热溶质对流存在的情况下可视化晶体学“锁定”共晶微观结构的发展。当共晶适应界面成分和生长速度的波动时，这些数据提供了对薄片到棒转变机制的直接了解。我们提供的证据表明这种转变是扩散性的。它是由作用在固-固-液三结点上的杂质驱动力引起的，必须克服固-固界面的刚度。我们的伪 4D 成像策略对凝固科学界具有广泛的吸引力，因为它可以克服传统原位 X 射线显微断层扫描中的时空权衡。(c) 2022 作者。由 Elsevier Ltd 代表 Acta Materialia Inc. 发布。这是一篇基于 CC BY 许可证的开放获取文章 (http://creativecommons.org/licenses/by/4.0/)
We investigate solidification of an Al-Cu alloy as a model system to understand the emergence of pat-terns (such as lamellar, rod and maze-like) within eutectic colonies. To uncover the morphological tran-sitions in situ and in 3D, we introduce here a new synchrotron-based procedure termed pseudo-4D X-ray imaging. Our method simultaneously maximizes the temporal (200 ms) and spatial resolution (0.69 2 mu m2/pixel) over that of traditional imaging approaches. The wealth of information obtained from this procedure enables us to visualize the development of a crystallographically 'locked' eutectic microstruc-ture in the presence of thermosolutal convection. This data provides direct insight into the mechanism of the lamella-to-rod transition as the eutectic accommodates fluctuations in interfacial composition and growth velocity. We offer evidence to show that this transition is diffusive. It is brought about by impurity-driven forces acting on the solid-solid-liquid trijunction that must overcome the stiffness of the solid-solid interfaces. Our pseudo-4D imaging strategy holds broad appeal to the solidification science community, as it can overcome the space-time trade-off in conventional in situ X-ray microtomography.(c) 2022 The Author(s). Published by Elsevier Ltd on behalf of Acta Materialia Inc.This is an open access article under the CC BY license ( http://creativecommons.org/licenses/by/4.0/ )