Dendrite growth velocity in levitated undercooled nickel melts
Dendrite growth velocity in levitated undercooled nickel melts
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DOI：
10.1016/j.jcrysgro.2006.08.045
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发表时间：
2006-12-15
影响因子：
1.8
通讯作者：
Herlach, D. M.
中科院分区：
文献类型：
--
作者：
Funke, O.;Phanikumar, G.;Herlach, D. M.
模型预测的枝晶生长速度在低过冷度偏离实验数据获得的电磁悬浮与电容接近传感器（CPS）[K。Eckler，D. M.赫拉赫，脱线。Sci. A 178（1994）159]。除此之外，以前通过不同技术获得的数据集彼此之间并不一致。例如，用高速照相机系统获得的镍熔体的生长速度数据[D. M.马特森，在：凝固1998，TMS，Warrendale PA，1998，第233页]显示在低过冷度下的值高于用CPS获得的数据。在这项工作中，在悬浮过冷镍样品的枝晶生长速度的新的测量作为过冷Δ T的函数进行调查这种差异。在30 K <Δ T < 300 K的过冷度范围内检测到过冷熔体的凝固。新的数据显示高精度和低散射。这些数据进行了比较，两个独立的增长速度数据集和差异进行了讨论。为了验证新的CPS数据，还通过使用高速相机测量了枝晶生长速度，其中研究了凝固前沿与样品表面的相交处的形态。根据Brener理论[E. Brener，J.Crystal Growth 99（1990）165]和目前正在开发的在凝固悬浮液滴中具有熔体对流的枝晶生长模型。特别注意对流和少量的杂质的生长动力学在小过冷度的影响。(c)2006年Elsevier BN。All rights reserved.
Model predictions for the dendrite growth velocity at low undercoolings are deviating significantly from experimental data obtained in electromagnetic levitation with a capacitance proximity sensor (CPS) [K. Eckler, D.M. Herlach, Mater. Sci. Eng. A 178 (1994) 159]. In addition to that, previous data sets obtained by different techniques are not in good agreement with each other. For instance, growth velocity data for nickel melts obtained with a high-speed camera system [D.M. Matson, in: Solidification 1998, TMS, Warrendale PA, 1998, p. 233] show higher values at low undercoolings than data obtained with the CPS. Within this work new measurements of dendritic growth velocity in levitated undercooled nickel samples were performed as a function of undercooling Delta T to investigate this discrepancy. Solidification of the undercooled melt was detected at undercooling levels within the range of 30 K < Delta T < 300 K. The new data reveal high accuracy and low scattering. These data are compared with two independent growth velocity data sets and discrepancies are discussed. For verification of the new CPS data dendrite growth velocity was also measured by using a high-speed camera where the morphology of the intersection of the solidification front with the sample surface was investigated. The new experimental data are analyzed within the model of dendrite growth obtained on the basis of Brener's theory [E. Brener, J. Crystal Growth 99 (1990) 165] and the model of dendrite growth with melt convection in a solidifying levitated drop, presently being developed. Special attention is paid to the effects of convection and small amounts of impurities on the growth dynamics at small undercoolings. (c) 2006 Elsevier BN. All rights reserved.