Microstructural characterization of cobalt-antimony eutectic alloy droplets solidified in drop tube

被引:24
作者
Cao, CD [1 ]
Xie, WJ [1 ]
Wei, B [1 ]
机构
[1] Northwestern Polytech Univ, Dept Appl Phys, Lab Mat Sci Space, Xian 710072, Peoples R China
来源
MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING | 2000年 / 283卷 / 1-2期
基金
中国国家自然科学基金;
关键词
rapid solidification; microstructure; dendrite growth; eutectic growth; grain refinement;
D O I
10.1016/S0921-5093(99)00797-2
中图分类号
TB3 [工程材料学];
学科分类号
0805 ; 080502 ;
摘要
Co-Sb alloy droplets have been solidified during free fall in a 3 m drop tube. The cooling rate and undercooling are estimated versus droplet diameter, both of which play a dominant part in dendritic and eutectic growth. The eutectic coupled zone has been calculated on the basis of TMK and LKT/BCT theories, which covers a composition range from 22.7% to 49%Sb. A lamellar-anomalous' eutectic transition occurs to Co-41.3%Sb droplets with the increase of undercooling. For Co-20%Sb hypoeutectic alloy, primary alpha-Co phase experiences a 'dendritic to equiaxed' structural morphology transition and an abrupt grain refinement at a critical undercooling of about 88 K under drop tube conditions. The remaining interdendritic liquid does not solidify in a mode of eutectic growth but forms into a divorced structure under drop tube conditions. The primary beta-CoSb intermetallic compound of Co-45%Sb hypereutectic alloy grows in a dendritic way inside droplet and forms as a spherical shell on droplet surface. Most Co-45%Sb droplets undercooled by 80 - 130 K exhibit complete eutectic microstructures. Significant solute trapping takes place in primary alpha-Co and beta-CoSb dendrites. (C) 2000 Elsevier Science S.A. All rights reserved.
引用
收藏
页码:86 / 93
页数:8
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