Rapid solidification and liquid-phase separation of undercooled CoCrCuFexNi high-entropy alloys

The liquid phase separation (LPS) behavior in Co-Cr-based high-entropy alloys (HEAs) is an important target for the development of Co-Cr-based HEAs for metallic biomaterials (BioHEAs). The solidification microstructure in Ag-Co-Cr-Fe-Mn-Ni-Ag, Co-Cr-Cu-Fe-Mn-Ni-Cu, and Co-Cr-Cu-Fe-Mn-Ni-B HEAs, which were designed as the combination of the equiatomic CoCrFeMnNi with Ag, Cu, and the interstitial element of B, was investigated as the fundamental research of LPS in Co-Cr-based HEAs. Ingots of equiatomic AgCoCrFeMnNi, equiatomic CoCrCuFeMnNi, non-equiatomic CoCrCuxFeMnNi (x = 2, 3), and CoCrCuxFeMnNiB0.2 (x = 1, 2, 3) with a small amount of B were fabricated using the arc-melting process. A macroscopic phase-separated structure was observed in the ingots of the equiatomic AgCoCrFeMnNi and CoCrCuxFeMnNiB0.2 (x = 2, 3) HEAs. The addition of a small amount of B enhanced the LPS tendency in the Co-Cr-Fe-Mn-Ni-Cu HEAs. The LPS behavior was discussed through the heat of mixing and computer coupling of phase diagrams and thermochemistry (CALPHAD).

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Microstructures and liquid phase separation in multicomponent CoCrCuFeNi high entropy alloys

Materials Science and Technology ◽

10.1179/1743284715y.0000000127 ◽

2016 ◽

pp. 1-5 ◽

Cited By ~ 13

Author(s):

P. H. Wu ◽

N. Liu ◽

P. J. Zhou ◽

Z. Peng ◽

W. D. Du ◽

...

Keyword(s):

Phase Separation ◽

Liquid Phase ◽

Liquid Phase Separation ◽

High Entropy Alloys ◽

High Entropy

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Liquid phase separation in transition element high entropy alloys

Intermetallics ◽

10.1016/j.intermet.2017.03.015 ◽

2017 ◽

Vol 86 ◽

pp. 59-72 ◽

Cited By ~ 25

Author(s):

A. Munitz ◽

M.J. Kaufman ◽

R. Abbaschian

Keyword(s):

Phase Separation ◽

Liquid Phase ◽

Transition Element ◽

Liquid Phase Separation ◽

High Entropy Alloys ◽

High Entropy

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Microstructure of Co-Cr-Fe-Mn-Ni-Cu and Co-Cr-Fe-Mn-Ni-Ag High Entropy Alloys with Liquid Phase Separation

Materials Science Forum ◽

10.4028/www.scientific.net/msf.941.1238 ◽

2018 ◽

Vol 941 ◽

pp. 1238-1241 ◽

Cited By ~ 4

Author(s):

Takeshi Nagase

Keyword(s):

Phase Separation ◽

Liquid Phase ◽

Condensed Matter ◽

Liquid Phase Separation ◽

High Entropy Alloys ◽

Common Phenomenon ◽

High Entropy ◽

Dendritic Structures

Liquid phase separation is a common phenomenon observed in various types of condensed matter, including metals. The microstructure of Co-Cr-Mn-Fe-Ni-Cu and Co-Cr-Fe-Mn-Ni-Ag high entropy alloys (HEAs) with liquid phase separation was investigated. Dual fcc phases were observed in CoCrFeMnNiAg, CoCrFeMnNiCu, and CoCrFeMnNiCu2HEAs. A macroscopically phase separated structure formed via liquid phase separation was observed in CoCrFeMnNiAg HEA, and conventional dendritic structures were observed in CoCrFeMnNiCu and CoCrFeMnNiCu2HEAs.

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Liquid Phase Separation in High-Entropy Alloys—A Review

Entropy ◽

10.3390/e20110890 ◽

2018 ◽

Vol 20 (11) ◽

pp. 890 ◽

Cited By ~ 12

Author(s):

Nicholas Derimow ◽

Reza Abbaschian

Keyword(s):

Phase Separation ◽

Liquid Phase ◽

Liquid Phase Separation ◽

Miscibility Gap ◽

Mixing Enthalpy ◽

High Entropy Alloys ◽

High Entropy ◽

Entropy Of Mixing ◽

Miscibility Gaps ◽

Alloy Systems

It has been 14 years since the discovery of the high-entropy alloys (HEAs), an idea of alloying which has reinvigorated materials scientists to explore unconventional alloy compositions and multicomponent alloy systems. Many authors have referred to these alloys as multi-principal element alloys (MPEAs) or complex concentrated alloys (CCAs) in order to place less restrictions on what constitutes an HEA. Regardless of classification, the research is rooted in the exploration of structure-properties and processing relations in these multicomponent alloys with the aim to surpass the physical properties of conventional materials. More recent studies show that some of these alloys undergo liquid phase separation, a phenomenon largely dictated by low entropy of mixing and positive mixing enthalpy. Studies posit that positive mixing enthalpy of the binary and ternary components contribute substantially to the formation of liquid miscibility gaps. The objective of this review is to bring forth and summarize the findings of the experiments which detail liquid phase separation (LPS) in HEAs, MPEAs, and CCAs and to draw parallels between HEAs and the conventional alloy systems which undergo liquid-liquid separation. Positive mixing enthalpy if not compensated by the entropy of mixing will lead to liquid phase separation. It appears that Co, Ni, and Ti promote miscibility in HEAs/CCAs/MPEAs while Cr, V, and Nb will raise the miscibility gap temperature and increase LPS. Moreover, addition of appropriate amounts of Ni to CoCrCu eliminates immiscibility, such as in cases of dendritically solidifying CoCrCuNi, CoCrCuFeNi, and CoCrCuMnNi.

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Liquid-phase separation of immiscible CrCuxFeMoyNi high-entropy alloys

Materials Science and Technology ◽

10.1080/02670836.2017.1290736 ◽

2017 ◽

Vol 33 (11) ◽

pp. 1352-1359 ◽

Cited By ~ 13

Author(s):

Z. Peng ◽

N. Liu ◽

S. Y. Zhang ◽

P. H. Wu ◽

X. J. Wang

Keyword(s):

Phase Separation ◽

Liquid Phase ◽

Liquid Phase Separation ◽

High Entropy Alloys ◽

High Entropy

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Liquid phase separation in undercooled Cu–Co alloys under the influence of static magnetic fields

Philosophical Transactions of The Royal Society A Mathematical Physical and Engineering Sciences ◽

10.1098/rsta.2018.0207 ◽

2019 ◽

Vol 377 (2143) ◽

pp. 20180207 ◽

Cited By ~ 5

Author(s):

Dandan Zhao ◽

Jianrong Gao

Keyword(s):

Phase Separation ◽

Liquid Phase ◽

Magnetic Fields ◽

Rapid Solidification ◽

Superconducting Magnet ◽

Optical Microscope ◽

Liquid Phase Separation ◽

Static Magnetic Fields ◽

Phase Separation Kinetics ◽

Bottom Side

Undercooling of Cu-based alloys often induces metastable liquid phase separation followed by rapid solidification of separated liquids. The rapid solidification can help freeze in the morphology of a higher-melting liquid and eases difficulties in studies of liquid phase separation kinetics. In the present work, the influence of static magnetic fields on liquid phase separation in bulk Cu 84 Co 16 composition was investigated. Inductively melted samples were glass-fluxed, undercooled and solidified under uniform and non-uniform magnetic fields generated by a superconducting magnet. Solidification microstructure of the phase-separated samples was examined using an optical microscope. The imposition of the magnetic fields, both uniform and non-uniform, altered the morphology, segregation pattern and size distribution of Co-rich droplets due to liquid phase separation. The imposition of the non-uniform magnetic fields with positive and negative gradients brought about segregation of the Co-rich droplets at the top and the bottom side of the samples, respectively. Such influence of the static magnetic fields is interpreted by assuming intensification of convective flow and Kelvin force-controlled migration of the Co-rich droplets. This article is part of the theme issue ‘Heterogeneous materials: metastable and non-ergodic internal structures’.

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