Revealing the mechanisms by which magneto-hydrodynamics disrupts solidification microstructures
Revealing the mechanisms by which magneto-hydrodynamics disrupts solidification microstructures
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DOI：
10.1016/j.actamat.2020.06.041
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发表时间：
2020-09
期刊：
影响因子：
9.4
通讯作者：
B. Cai;A. Kao;E. Boller;O. Magdysyuk;R. Atwood;Nghia T. Vo;K. Pericleous;P. Lee
中科院分区：
文献类型：
--
作者：
B. Cai;A. Kao;E. Boller;O. Magdysyuk;R. Atwood;Nghia T. Vo;K. Pericleous;P. Lee
磁流体动力学（MHD）是控制凝固组织的一项关键技术，它是通过施加磁场对金属和合金进行凝固而产生的。应用范围从散装搅拌到流动控制和湍流阻尼通过诱导洛伦兹力。在过去的二十年里，由热电电流和磁场相互作用引起的洛伦兹力，一种被称为热电磁流体动力学（TEMHD）的MHD现象，也被证明可以驱动树枝状流动改变微观结构的演变。在这项贡献中，高速同步加速器x射线断层扫描和高性能计算模拟相结合，揭示了磁场内凝固的演变，动力学和机制，解决了不同来源的洛伦兹力引起的复杂相互作用和竞争流动效应。这项研究使我们能够揭示破坏传统柱状枝晶凝固微观结构的机制，从阿基米德螺旋状结构到高度精细的枝晶初级阵列。我们还证明，合金成分可以根据塞贝克系数和初生相和枝晶间液体的相对密度来增加或减少MHD的影响。这项工作为开发和优化MHD在凝固过程中的应用以及利用这些力的新型合金的计算设计铺平了新的计算和实验方法。
A key technique for controlling solidification microstructures is magneto-hydrodynamics (MHD), resulting from imposing a magnetic field to solidifying metals and alloys. Applications range from bulk stirring to flow control and turbulence damping via the induced Lorentz force. Over the past two decades the Lorentz force caused by the interaction of thermoelectric currents and a magnetic field, a MHD phenomenon known as Thermoelectric Magnetohydrodynamics (TEMHD), was also shown to drive inter-dendritic flow altering microstructural evolution. In this contribution, high-speed synchrotron X-ray tomography and high-performance computational simulation are coupled to reveal the evolution, dynamics and mechanisms of solidification within a magnetic field, resolving the complex interplay and competing flow effects arising from Lorentz forces of different origins. The study enabled us to reveal the mechanisms disrupting the traditional columnar dendritic solidification microstructure, ranging from an Archimedes screw-like structure, to one with a highly refined dendritic primary array. We also demonstrate that alloy composition can be tailored to increase or decrease the influence of MHD depending on the Seebeck coefficient and relative density of the primary phase and interdendritic liquid. This work paves the way towards novel computational and experimental methods of exploiting and optimising the application of MHD in solidification processes, together with the calculated design of novel alloys that utilise these forces.