期刊
INTERMETALLICS
卷 72, 期 -, 页码 44-52出版社
ELSEVIER SCI LTD
DOI: 10.1016/j.intermet.2016.01.008
关键词
rapid solidification; high-entropy alloys; microstructure; phase transformation; nanocrystalline structure
资金
- National Natural Science Foundation of China [51201072, 51471079]
- Qinglan Project of Jiangsu Provence
- Graduate Student Innovation Projects of Jiangsu University of Science and Technology [YSJ14S-15]
- Graduate Student Innovation Projects of Jiangsu Province [SJLX15-0530]
- Priority Academic Program Development of Jiangsu Higher Education Institutions
Fluxing and cyclic superheating technique was used to investigate the rapid solidification behavior of CoCrCuFexNi (x = 1.0, 1.5, 2.0, molar concentration) high-entropy alloys in this study. The microstructures of CoCrCuFexNi (x = 1.0, 1.5, 2.0) high-entropy alloys solidified at different undercoolings (Delta T) were investigated. Liquid-phase separation leading to Cu-rich and Cu-depleted regions, were obtained in the solidified microstructure from highly undercooled melt. This occurs when the melt undercooling exceeds a critical undercooling (Delta T-crit) of 160 K for CoCrCuFeNi, 190 K for CoCrCuFe1.5Ni and 293 K for CoCrCu-Fe2Ni alloy. However, typical dendrites and interdendritic regions were observed in rapid-solidified CoCrCuFexNi alloys prepared from melts with a small undercooling (Delta T < Delta T-crit). Conversely, a large amount of Cu-rich spheres and even egg-type structures were observed in alloys solidified from melts with large degree of undercooling, Delta T in excess of the critical value, Delta T-crit. A large amount of Cu-rich nano-phases were found in the matrix, possibly, due to the precipitation of Cu-rich phase from the supersaturated solid solution obtained during solidification. The positive enthalpies of mixing between Cu and the other elements in the multi-component alloys resulted in the occurrence of liquid-phase separation prior to the liquid-solid transformation starts. The sluggish diffusion effect of high-entropy alloys and rapid solidification play an important part in the precipitation of nanophase during the solid-state transformation in the Cu-based matrix. Similar to other immiscible alloys, liquid-phase separation occurred when a critical undercooling was exceeded. Differently, nanophases were found in the microstructures of multi-component CoCrCuFexNi (x = 1.0, 1.5, 2.0) alloys. (C) 2016 Elsevier Ltd. All rights reserved.
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