Microstructure formation and in situ phase identification from undercooled Co-61.8 at.% Si melts solidified on an electromagnetic levitator and an electrostatic levitator
Microstructure formation and in situ phase identification from undercooled Co-61.8 at.% Si melts solidified on an electromagnetic levitator and an electrostatic levitator
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DOI：
10.1016/j.actamat.2008.01.041
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发表时间：
2008-06
期刊：
影响因子：
9.4
通讯作者：
Mingjun Li;K. Nagashio;T. Ishikawa;A. Mizuno;M. Adachi;Masahito Watanabe;S. Yoda;K. Kuribayashi-K.-Kuribayas
中科院分区：
文献类型：
--
作者：
Mingjun Li;K. Nagashio;T. Ishikawa;A. Mizuno;M. Adachi;Masahito Watanabe;S. Yoda;K. Kuribayashi-K.-Kuribayas
有限公司- 61.8。在不同过冷度的电磁悬浮器（EML）和静电悬浮器（ESL）上对% Si （CoSi-CoSi2）共晶合金进行了固化。结果表明，在低过冷条件下，以CoSi金属间化合物为初相，在EML或ESL上只发生单一的回发光事件，与加工设备无关。然而，微观结构强烈地依赖于加工设备。在EML下凝固的球体内部熔体流动行为与在ESL下有很大的不同，从而产生不同的微观结构。在高过冷时，无论悬浮条件如何，都会发生双回热。在EML上凝固的合金的原位x射线衍射表明，cosi2化合物在第一次再发光时成为初级相，CoSi金属间相在第二次再发光时结晶。除了相识别之外，实时衍射图还可以提供半固态冷却过程中初生相破碎和成熟特征的额外证据。在考虑成核势垒时，讨论了CoSi和cosi2化合物之间的相竞争。cosi2相较低的界面能有利于CoSi相的优先成核，这也在非互易成核中起关键作用，从而在高过冷时产生双回热。
Co–61.8at.% Si (CoSi–CoSi2) eutectic alloys were solidified on an electromagnetic levitator (EML) and an electrostatic levitator (ESL) at different undercooling levels. The results indicated that there is only a single recalescence event at low undercooling with the CoSi intermetallic compound as primary phase, which is independent of processing facilities, on either an EML or an ESL. The microstructure, however, is strongly dependent on the processing facility. The interior melt flow behavior in the sphere solidified at the EML differs substantially from that at the ESL, thus yielding different microstructures. On high undercooling, double recalescence takes place regardless of levitation condition. In situ X-ray diffraction of alloys solidified on the EML demonstrates that the CoSi2compound becomes the primary phase upon the first recalescence, and the CoSi intermetallic phase crystallizes during the second recalescence. In addition to phase identification, real-time diffraction patterns can also provide additional evidence of the fragmentation of the primary phase and the ripening feature in the subsequent cooling process in the semisolid state. The phase competition between the CoSi and CoSi2compounds is discussed when considering the nucleation barrier. The low interfacial energy of the CoSi2phase favors a preferential nucleation event over the CoSi phase, which also plays a critical role in non-reciprocity nucleation and thus yields a double recalescence profile at high undercooling.