静电悬浮下铌异质形核及枝晶生长  

Heterogeneous nucleation and dendritic growth of niobium under containerless electrostatic levitation

作　　者：王艳秋 郑福 陆潇晓 孙志斌 Yan-qiu WANG;Fu ZHENG;Xiao-xiao LU;Zhi-bin SUN(National Space Science Center,Chinese Academy of Sciences,Beijing 100190,China;University of the Chinese Academy of Sciences,Beijing 101499,China)

机构地区：[1]中国科学院国家空间科学中心,北京100190 [2]中国科学院大学,北京101499

出　　处：《Transactions of Nonferrous Metals Society of China》2024年第4期1333-1346,共14页中国有色金属学报（英文版）

基　　金：supported by the Scientific Instrument Developing Project of the Chinese Academy of Sciences(No.YJKYYQ20190008);the Strategic Pioneer Program on Space Science,Chinese Academy of Sciences(No.XDA15013600);the Youth Innovation Promotion Association of the Chinese Academy of Sciences(Nos.2013105,Y201728)。

摘　　要：采用无容器静电悬浮实验技术,对纯度99.7%和99.95%铌材料的过冷程度和形核凝固机制进行了系统研究。通过经典形核理论分析测量和计算得到材料样品在形核和凝固过程的热物理参数和热动力学参数。实验结果统计分析表明:铌样品的最大过冷度为455.7 K,临界过冷度约为739 K。系统分析并计算得到铌样品最大概率形核过冷度、指前系数、成核活化能、固液界面自由能和关键晶核尺寸。样品的枝晶生长速度与过冷度呈幂函数关系,在过冷度454 K时,枝晶生长速度达到42.1 m/s。考虑非等温条件下界面能的各向异性对自由枝晶生长的影响,理论预测结果与实验获得实验结果一致。With the containerless electrostatic levitation method,the undercooling level and nucleation solidification mechanism of niobium samples of 99.7%and 99.95%in purity were comprehensively studied.The classical nucleation theory was used to measure and calculate the thermophysical and thermodynamic characteristics associated with the nucleation and solidification procedure.The measurement results show that the maximum undercooling of experimental samples is 455.7 K,while the hyper cooling limit of the niobium is derived at 739 K.The most probable nucleation undercooling,pre-exponential factor,nucleation activation energy,solid/liquid interface free energy,and the critical nucleus radius are determined.The dendrite growth velocity has a powerful relationship with undercooling,and the dendritic growth velocity of liquid niobium reaches 42.1 m/s at the undercooling of 454 K.The effect of the anisotropy of surface energy is taken into account,and the forecast results display excellent consistency with the experimental ones.

关 键 词：液态铌 异质形核 枝晶生长 形核凝固机制 无容器静电悬浮 

分 类 号：TG146.416[一般工业技术—材料科学与工程]