A new mechanism for freckle initiation based on microstructural level simulation
A new mechanism for freckle initiation based on microstructural level simulation
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DOI：
10.1016/j.actamat.2012.04.043
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发表时间：
2012-07
期刊：
影响因子：
9.4
通讯作者：
L. Yuan;P. Lee
中科院分区：
文献类型：
--
作者：
L. Yuan;P. Lee
采用微结构水平模型对铅锡合金定向凝固过程中的斑点形成过程进行了三维直接模拟。微观凝固模型解决了溶质分配、枝晶间热溶解对流、枝晶形成和重熔等复杂的相互作用。这些模拟表明，正是这些现象在微观结构水平上的竞争决定了溶质通道的启动和存活，从而决定了斑点形成的倾向。富含溶质的枝晶间流动使一次枝晶和二次枝晶都重新熔化，并使一次枝晶偏转。这使得溶解通道能够自我维持，形成雀斑。然后将该微观结构模型应用于临界瑞利数的预测，与大量的实验数据进行了很好的吻合，显示了该模型在新的合金系统和凝固过程中的应用潜力。
Freckle formation was directly simulated in three dimensions with a microstructure level model for unidirectional solidified Pb–Sn alloys. The microscale solidification model resolves the complex interaction of solute partition, interdendritic thermosolutal convection, dendrite formation and remelting. These simulations show that it is competition between all off these phenomena at the microstructural level that determines both the initiation and survival of solute channels and, hence, the propensity for freckle formation. The solute enriched interdendritic flow remelts both primary and secondary arms, and can deflect the primaries. This enables solutal channels to become self-sustaining, forming freckles. The microstructural model was then applied to predict the critical Rayleigh number, with excellent agreement with a large range of experimental data, demonstrating its potential for applications to new alloy systems and solidification processes.