Multiphysics Modelling of Ultrasonic Melt Treatment in the Hot-Top and Launder during Direct-Chill Casting: Path to Indirect Microstructure Simulation
Multiphysics Modelling of Ultrasonic Melt Treatment in the Hot-Top and Launder during Direct-Chill Casting: Path to Indirect Microstructure Simulation
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DOI：
10.3390/met11050674
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发表时间：
2021-05-01
期刊：
影响因子：
2.9
通讯作者：
Tzanakis, Iakovos
中科院分区：
文献类型：
--
作者：
Beckwith, Christopher;Djambazov, Georgi;Tzanakis, Iakovos
研究了两种相互竞争的超声处理(UST)策略在铝合金直接激冷(DC)铸造过程中细化组织的数值模拟。在第一种更常规的情况下，将振动频率为17.3 kHz的声波电极浸入顶部以处理水池熔池，在第二种情况下，将声波电极插入洗衣机的挡板之间。已知的组织细化取决于声空化的强度和被处理流体在空化区的停留时间。几何形状、声场强度、诱导流速和局部温度是影响该处理的因素。在这项工作中建立的数学模型将流动速度、声学在宏观尺度上的空化、传热和凝固与拉格朗日细化剂颗粒相结合，用于确定：(A)它们在活跃区的停留时间，以及(B)它们作为速度场的函数在水池中的最终分布。这是首次尝试将颗粒模型作为替代显微组织模拟的一种有效的间接方法，结果表明，在挡板分离器的辅助下，在熔池中使用UST可以产生更均匀的细化颗粒分布，避免了伴随热顶处理而产生的强烈声流射流，并可能导致细化颗粒的强烈偏析。与这项工作中的数值研究平行进行的实验似乎支持在模拟中获得的结果。
This study concerns the numerical simulation of two competing ultrasonic treatment (UST) strategies for microstructure refinement in the direct-chill (DC) casting of aluminium alloys. In the first, more conventional, case, the sonotrode vibrating at 17.3 kHz is immersed in the hop-top to treat the sump melt pool, in the second case, the sonotrode is inserted between baffles in the launder. It is known that microstructure refinement depends on the intensity of acoustic cavitation and the residence time of the treated fluid in the cavitation zone. The geometry, acoustic field intensity, induced flow velocities, and local temperature are factors which affect this treatment. The mathematical model developed in this work couples flow velocity, acoustics modified by cavitation, heat transfer, and solidification at the macroscale, with Lagrangian refiner particles, used to determine: (a) their residence time in the active zones, and (b) their eventual distribution in the sump as a function of the velocity field. This is the first attempt at using particle models as an efficient, though indirect, alternative to microstructure simulation, and the results indicate that UST in the launder, assisted with baffle separators, yields a more uniform distribution of refining particles, avoiding the strong acoustic streaming jet that, otherwise, accompanies hot-top treatment, and may lead to the strong segregation of refining particles. Experiments conducted in parallel to the numerical studies in this work appeared to support the results obtained in the simulation.