The spatial and temporal distribution of dendrite fragmentation in solidifying Al-Cu alloys under different conditions
The spatial and temporal distribution of dendrite fragmentation in solidifying Al-Cu alloys under different conditions
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DOI：
10.1016/j.actamat.2016.09.013
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发表时间：
2016-12-01
期刊：
影响因子：
9.4
通讯作者：
Grant, P. S.
中科院分区：
文献类型：
--
作者：
Liotti, E.;Lui, A.;Grant, P. S.
采用同步辐射X射线原位研究了Al-Cu合金定向柱状晶凝固过程中，在无脉冲电磁场和有脉冲电磁场作用下，不同凝固方向上枝晶破碎的时空分布。不同的安排有一个强大的和可重复的影响碎裂行为，合理化使用的模型溶质驱动重熔的枝晶臂的微观结构区域的高脆弱性。虽然破碎的绝对速率各不相同，但所有的破碎分布在进入糊状区的500-800 pm处具有破碎速率的特征峰。与用于枝晶根部重熔的溶质富集液体流的需要一致，该峰被解释为在存在直接从射线照片测量的相对陡峭的液体溶质浓度梯度和枝晶网络对液体流的相对高的渗透性的条件下发生。皇冠版权所有（C）2016由爱思唯尔有限公司代表Acta Materialia Inc. All rights reserved.
The directional columnar solidification of Al-Cu alloy dendrites was studied in-situ by synchrotron X-ray radiography to investigate the spatial and temporal distribution of dendrite fragmentation, without and with an applied pulsed electromagnetic field (PEMF) and in different solidification directions. The differing arrangements had a strong and reproducible influence on fragmentation behaviour that was rationalised using a model of solute-driven re-melting of dendrite arms in microstructural regions of high vulnerability. Although absolute rates of fragmentation varied, all the fragmentation distributions had a characteristic peak in fragmentation rate at a distance of 500-800 pm into the mushy zone. Consistent with the need for solute-rich liquid flow for dendrite root re-melting, this peak was explained to occur under conditions where there was both comparatively steep liquid solute concentration gradients, measured directly from the radiographs, and relatively high permeability of the dendrite network to liquid flow. Crown Copyright (C) 2016 Published by Elsevier Ltd on behalf of Acta Materialia Inc. All rights reserved.