Mesoscopic Simulation of Dendritic Growth Observed in X-ray Video Microscopy During Directional Solidification of Al-Cu Alloys
Mesoscopic Simulation of Dendritic Growth Observed in X-ray Video Microscopy During Directional Solidification of Al-Cu Alloys
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DOI：
10.2355/isijinternational.50.1886
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发表时间：
2010-12
影响因子：
1.8
通讯作者：
Pierre Delaleau;C. Beckermann;R. Mathiesen;L. Arnberg
中科院分区：
文献类型：
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作者：
Pierre Delaleau;C. Beckermann;R. Mathiesen;L. Arnberg
开发了介观模型来模拟 Hele-Shaw 槽中 Al-Cu 合金定向凝固过程中通过 X 射线视频显微镜现场观察到的微观结构。在该模型中，求解体积平均物质守恒方程以获得溶质浓度和固体分数场，并使用分析停滞膜模型来预测枝晶包络的运动。该模型在多个测试用例中经过仔细验证。然后，应用该模型模拟两种不同合金成分的 X 射线视频显微镜实验中观察到的柱状枝晶微观结构。测量的和预测的枝晶包络形状、固体分数和溶质浓度场之间存在合理的一致性。预测的糊状区域的大小和柱状前缘之前的过冷熔融区域的范围与原位实验观察结果非常吻合。模拟结果显示与从射线照片测量的内部固体分数变化定量一致。本模型还能够真实地模拟在其中一项实验中观察到的初级树突主干间距调整。总体而言，本研究首次使用金属合金实验的实时原位数据成功验证了凝固模型。需要大量的额外研究来解释模型中重力驱动熔体对流的影响。
A mesoscopic model is developed to simulate microstructures observed in situ by X-ray video microscopy during directional solidification of Al–Cu alloys in a Hele–Shaw cell. In the model, a volume-averaged species conservation equation is solved to obtain the solute concentration and solid fraction fields, and an analytical stagnant film model is used to predict the motion of the dendrite envelopes. The model is carefully validated in several test cases. Then, the model is applied to simulate the columnar dendritic microstructures observed in the X-ray video microscopy experiments for two different alloy compositions. Reasonable agreement is found between the measured and predicted dendrite envelope shapes, solid fractions, and solute concentration fields. The predicted size of the mushy zone and the extent of the undercooled melt region ahead of the columnar front agree well with the in situ experimental observations. The simulation results show quantitative agreement with the internal solid fraction variations measured from the radiographs. The present model is also able to realistically simulate a primary dendrite trunk spacing adjustment that was observed in one of the experiments. Overall, the present study represents the first successful validation of a solidification model using real time, in situ data from an experiment with a metallic alloy. Considerable additional research is needed to account in the model for the effect of gravity driven melt convection.