Structural evidence for the transition from coupled to decoupled growth in the solidification of undercooled Ni-Sn eutectic melt
Structural evidence for the transition from coupled to decoupled growth in the solidification of undercooled Ni-Sn eutectic melt
复制标题
过冷镍锡共晶熔体凝固过程中从耦合生长到解耦生长转变的结构证据
DOI：
10.1007/s11661-007-9198-2
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发表时间：
2007-08-01
影响因子：
2.8
通讯作者：
Zhou, Y. H.
中科院分区：
文献类型：
--
作者：
Li, J. F.;Jie, W. Q.;Zhou, Y. H.
Ni-18.7 at. PET Sri共晶熔体在玻璃熔剂的包裹中过冷并自发固化。系统地研究了样品表面和样品内部的组织形貌，并清楚地揭示了合金的临界过冷度为130 K。在临界过冷度以下，耦合的层状共晶（α-Ni和β-Ni 3Sn）在过冷熔体中枝晶生长。超过临界过冷度，a-Ni枝晶首先形成在早期的冷却。β-Ni 3Sn在剩余的液体中均匀成核，然后与α-Ni单独生长。剩余的液相凝固成层状共晶只发生在样品表层中a-Ni枝晶臂之间的空间足够大的地方。过冷度高于20 K时的凝固组织均为异常共晶组织，表明在快速凝固过程中，共晶生长和枝晶生长的耦合作用都可能导致异常共晶组织的形成。结果还表明，当过冷度超过50 K时，通过观察吸热峰来测量该合金的晶体生长速度是可行的。
Ni-18.7 at. pet Sri eutectic melt was undercooled and spontaneously solidified In the encasement of a glass flux. Structure morphologies of the sample surface as well as inside the sample were systematically examined, and a critical undercooling of 130 K was clearly revealed for the alloy. Below the critical undercooling, coupled lamellar eutectics (alpha-Ni and beta-Ni3Sn) dendritically grow in the undercooled melt. Beyond the critical undercooling, a-Ni dendrites first form during the early recalescence. beta-Ni3Sn nucleates uniformly in the remaining liquid and then separately grows with alpha-Ni. Solidification of the remaining liquid into lamellar eutectics only occurs at the places in the sample surface layer where the space between the a-Ni dendrite arms is large enough. The finding that all the solidification structures at undercooling above 20 K comprise anomalous eutectics indicates that both coupled eutectic growth and decoupled dendritic growth in the rapid solidification can result in the anomalous eutectic formation. The results also indicate that it is feasible to measure the crystal growth velocity by observation of the recalescence front when undercooling exceeds 50 K for this alloy.