Competitive Nucleation and Rapid Growth of Co-Si Intermetallic Compounds during Eutectic Solidification under Containerless Processing Condition

Wenjing Yao1), Zipeng Ye1), Nan Wang1), Xiujun Han2), Jianyuan Wang1) and Xixing Wen1) 1) Department of Applied Physics, Northwestern Polytechnical University, Xi an 710072, China 2) School of Materials Science, Shanghai Jiaotong University, Shanghai 200240, China

摘 要：The liquid-solid transitions of （Co2Si+CoSi） and （CoSi+CoSi2） eutectic alloys were realized in drop tube and the rapid eutectic growth mechanism of intermetallic compounds was examined. The experimental and calculated results indicate that with increasing Co content, the intermetallic compound prefers nucleating primarily. The eutectic microstructures experience the transitions of ’lamellar-anomalous-divorced’ eutectic with undercooling. In undercooled state, the growth of CoSi intermetallic compound always lags behind others, and no matter how large the undercooling is, this intermetallic compound grows under the solutal diflusion control. The calculated coupled zone demonstrates that （Co2Si+CoSi） eutectic can form within certain undercooling regime, when the composition is in the range from 23.6% to 25.4% Si. And the calculated coupled zone of （CoSi+CoSi2） covers a composition range from 40.8% to 43.8% Si.

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