Observation of dendrite growth velocity and microstructure transition in highly undercooled single phase alloys
Observation of dendrite growth velocity and microstructure transition in highly undercooled single phase alloys
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高过冷单相合金枝晶生长速度和显微组织转变的观察
DOI：
10.1016/j.matchar.2019.109793
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发表时间：
2019-09
影响因子：
4.7
通讯作者：
Hua Hou
中科院分区：
文献类型：
--
作者：
Xiaolong Xu;Yuhong Zhao;Hua Hou
利用高速热成像技术，系统研究了Ni90Cu10和Ni95Cu5单相合金熔体初始过冷时枝晶生长速度的变化规律。对于这两种非稀浓合金，枝晶生长速度在小过冷和中过冷状态下先连续增加，然后在高过冷状态下不连续地达到最大值。生长速度-过冷曲线呈明显的平台型，由溶质控制为主逐渐过渡到热控制为主，与稀合金的凝固特征非常相似。生长速度-过冷关系的不连续性是由于固体熔体中溶质扩散速度有限而导致的。利用EBSD技术对两种过冷合金的组织、亚结构和显微组织进行了表征，并对“自发晶粒细化”的基本机理进行了探讨。显微组织演变为两种细化：一种是枝晶重熔诱导的晶粒细化，另一种是再结晶诱导的晶粒细化。结果表明，随着初始体积过冷量的增加，凝固态组织的织构变得越来越随机，这是由于凝固态组织中应力和再结晶的增加所致。在凝固态样品中发现了晶粒细化的新证据。我们发现过冷后的样品具有晶粒细化的组织，这与枝晶生长速度-过冷曲线的明显不连续相对应。显微组织数据表明，Ni-Cu合金在高过冷状态下的晶粒细化是再结晶过程的结果，而传统的晶粒细化合金的晶粒细化似乎是重熔诱导的枝晶断裂的结果。
Dendrite growth velocity as a function of initial bulk undercooling was systematically studied in situ using high speed thermal imaging of highly undercooled Ni90Cu10 and Ni95Cu5 single phase alloy melts. For these two non-dilute concentrated alloys, the dendrite growth velocity first increased continuously at small and mediate undercooling regimes and then discontinuously to a maximum value at the high undercooling range. A clear plateau appeared in the growth velocity-undercooling curve revealed a gradual transition from mainly solute-controlled growth to mainly thermal-controlled growth, which was very similar to the solidification characteristics of a dilute alloy. The discontinuity appeared in the growth velocity-undercooling relationship was suggested to be induced by the finite solute diffusion speed in the bulk melt ahead of the advancing solid-liquid interface. Microstructure, substructure and microtexture of the two undercooled alloys were characterized using EBSD technique, and the fundamental mechanism behind “spontaneous grain refinement” is elucidated. The microstructure evolution indicated two kinds of grain refinements: one was dendrite remelting induced grain refinement and the other was recrystallization induced grain refinement. It was found that the texture of the as-solidified microstructure was getting more and more random as the initial bulk undercooling increased, which was due to the increased stress and recrystallization in the as-solidified microstructure. New evidence of grain refinement was found in the as-solidified samples. We found that the samples undercooled beyond the critical undercooling had a grain refined microstructure and that this corresponded with a clear discontinuity in the dendrite growth velocity-undercooling curve. Microstructural data suggested that in Ni-Cu alloys grain refinement at a high undercooling was a consequence of a recrystallization process, which contrasted with conventional grain refined alloys where grain refinement appeared to be the result of remelting-induced dendritic fragmentation.
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影响因子：
4.4
作者：
H. Hou;Zhiqin Wen;Yu-hong Zhao;L. Fu;Nan Wang;Peide Han
通讯作者：
H. Hou;Zhiqin Wen;Yu-hong Zhao;L. Fu;Nan Wang;Peide Han
影响因子：
6.2
作者：
Xiaolong Xu;Yu-hong Zhao;H. Hou;Feng Liu
通讯作者：
Xiaolong Xu;Yu-hong Zhao;H. Hou;Feng Liu
影响因子：
1.8
作者：
P. Galenko;D. Danilov
通讯作者：
P. Galenko;D. Danilov
影响因子：
3.2
作者：
A. Mullis;R. Cochrane
通讯作者：
A. Mullis;R. Cochrane
DOI：
10.1016/j.msea.2006.02.435
发表时间：
2007-03
影响因子：
6.4
作者：
P. Galenko;Phanikumar Gandham;O. Funke;L. Chernova;S. Reutzel;M. Kolbe;D. Herlach
通讯作者：
P. Galenko;Phanikumar Gandham;O. Funke;L. Chernova;S. Reutzel;M. Kolbe;D. Herlach