Metastable solidification of hypereutectic Co2Si-CoSi composition: microstructural studies and in-situ observations☆
Metastable solidification of hypereutectic Co2Si-CoSi composition: microstructural studies and in-situ observations☆
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DOI：
10.1016/j.actamat.2017.09.037
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发表时间：
2018
期刊：
影响因子：
9.4
通讯作者：
Yeqing Wang;Jianrong Gao;M. Kolbe;A. Chuang;Yang Ren;D. Matson
中科院分区：
文献类型：
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作者：
Yeqing Wang;Jianrong Gao;M. Kolbe;A. Chuang;Yang Ren;D. Matson
采用显微组织和原位高能X射线衍射研究了过冷Co 60 Si 40熔体的亚稳凝固过程。确定了五种固化路径。其中三个是在低过冷度下观察到的，这表明稳定的β-Co_2Si和CoSi化合物的非耦合和耦合生长。其他路径观察到在高过冷度，这表明亚稳态Co 5Si 3化合物的围晶和初级结晶。β-Co2 Si和Co 5Si 3化合物结晶为六方晶体结构并经历固态分解。组织的形成取决于凝固路径，稳定化合物的耦合生长和非耦合生长分别产生规则的片层共晶组织和不规则的共晶组织。亚稳态Co 5Si 3化合物的晶化和固态分解形成了细晶两相混合物，这代表了另一种类型的异常共晶结构。结果提供了两种罕见的机制的异常共晶形成的证据，并阐明了亚稳相关系的Co单键Si系统的过冷区。
Metastable solidification of undercooled Co60Si40melts was investigated by microstructural studies and in-situ high-energy X-ray diffraction. Five solidification paths were identified. Three of them were observed at low undercoolings, which show uncoupled and coupled growth of stable β-Co2Si and CoSi compounds. The other paths were observed at high undercoolings, which show peritectic and primary crystallization of a metastable Co5Si3compound. The β-Co2Si and Co5Si3compounds crystallize into a hexagonal crystal structure and experience solid-state decomposition. Microstructure formation depends on solidification path. The coupled and uncoupled growth of the stable compounds produces a regular lamellar eutectic structure and an anomalous eutectic structure, respectively. The crystallization and solid-state decomposition of the metastable Co5Si3compound brings about a fine-grained two-phase mixture, which represents another type of anomalous eutectic structure. The results provide proof of two rare mechanisms of anomalous eutectic formation and shed light onto metastable phase relations in the undercooled region of the Cosingle bondSi system.