Dendrite coarsening during directional solidification of Al-Cu-Mn alloys
Dendrite coarsening during directional solidification of Al-Cu-Mn alloys
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DOI：
10.1016/s0921-5093(97)00720-x
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发表时间：
1998-06-01
期刊：
影响因子：
6.4
通讯作者：
Kattamis, TZ
中科院分区：
文献类型：
--
作者：
Chen, M;Kattamis, TZ
对Al-3.75%Cu-1.5%Mn和Al-1%Cu-1.5%Mn枝晶单晶的稳态定向凝固在淬火前中断不同长度的时间，并评估枝晶粗化动力学随温度的变化。对于一个给定的合金成分，等温粗化速率，表示为归一化比枝晶表面积的时间变化，随温度升高，随时间降低。它也随着铜浓度的增加而降低。二次枝晶臂间距随时间增加，并在较短的时间内，随着温度的降低。对于Al-3.75%Cu-1.5%Mn合金，这种趋势在超过约1.5 min的时间内发生逆转。对于所有时间，间距的增加速率均随温度而增加。凝固过程中，二次枝晶臂间距随着时间的推移而增加，并且生长速率逐渐降低。通过结合一个粗化模型，这是有效的粗化的早期阶段与一个模型，这是有效的后期阶段的比表面积对时间的依赖性预测合理。铜在液相中的扩散被认为是枝晶粗化的速率控制步骤。等温粗化过程中的二次臂间距的实验测量，以及在凝固过程中同意合理以及与模型预测。(C)1998年Elsevier Science S.A. All rights reserved.
Steady state directional solidification of Al-3.75%Cu-1.5%Mn and Al-1%Cu-1.5%Mn dendritic monocrystals was interrupted for different lengths of time prior to quenching and dendrite coarsening kinetics were evaluated versus temperature. For a given alloy composition, the isothermal coarsening rate, expressed as the time variation of the normalized specific dendrite surface area, increased with temperature and decreased with time. It also decreased with increasing copper concentration. The secondary dendrite arm spacing increased with time and for shorter times, with decreasing temperature. For Al-3.75%Cu-1.5%Mn alloy this trend was reversed for times exceeding about 1.5 min. For all times the rate of increase of the spacing increased with temperature. Secondary dendrite arm spacing increased with time during solidification and with decreasing growth rate. The dependence of specific surface area on time was predicted reasonably well by combining a coarsening model which is valid for the earlier stages of coarsening with a model which is valid for later stages. Copper diffusion through the liquid was found to be the rate controlling step in dendrite coarsening. Experimental measurements of secondary arm spacing during isothermal coarsening, as well as during solidification agreed reasonably well with model predictions. (C) 1998 Elsevier Science S.A. All rights reserved.