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论文类型：期刊论文

发表时间：2010-04-01

发表刊物：SCIENCE CHINA-TECHNOLOGICAL SCIENCES

收录刊物：SCIE、EI

卷号：53

期号：4

页面范围：1043-1048

ISSN号：1674-7321

关键字：interface structure; solidification; entropy; metals and alloys

摘要：Microstructure formation and transition of undercooled bulk Ni(70.2)Si(29.8) eutectic alloy melt were investigated by melt fluxing, cyclical overheating and cooling under high-frequency vacuum melting. The maximum undercooling of the alloy melt amounted to 428 K. Scanning electron microscope (SEM), energy-dispersive X-ray spectroscopy (EDS) and optical microscopy techniques (OM) were adopted to investigate the microstructure and identify the phase composition. The cooling curves of eutectic alloys upon solidification which were subjected to different undercoolings were described and compared. The complex microstructure evolution was observed in the as-solidified samples with the increase of undercooling. Surprisingly, an extremely fine microstructure was achieved at the max undercooling of 428 K, and the lamellar distance of about 50-100 nm was observed. Based on the solution entropy of eutectic phases, the microstructure transition with the undercooling was analyzed. Calculated results showed that the microstructure transition process was ascribed to solution entropy of transition, i.e., the complex microstructure evolution was attributed to a transition from faceted-faceted (FF) -> faceted-nonfaceted (FN) -> nonfaceted-nonfaceted (NN) eutectic systems concurring with increased undercooling.