The Grain Boundary Wetting Phenomena in the Ti-Containing High-Entropy Alloys: A Review

In this review, the phenomenon of grain boundary (GB) wetting by melt is analyzed for multicomponent alloys without principal components (also called high-entropy alloys or HEAs) containing titanium. GB wetting can be complete or partial. In the former case, the liquid phase forms the continuous layers between solid grains and completely separates them. In the latter case of partial GB wetting, the melt forms the chain of droplets in GBs, with certain non-zero contact angles. The GB wetting phenomenon can be observed in HEAs produced by all solidification-based technologies. GB leads to the appearance of novel GB tie lines Twmin and Twmax in the multicomponent HEA phase diagrams. The so-called grain-boundary engineering of HEAs permits the use of GB wetting to improve the HEAs’ properties or, alternatively, its exclusion if the GB layers of a second phase are detrimental.

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Grain Boundary Wetting by a Second Solid Phase in the High Entropy Alloys: A Review

Materials ◽

10.3390/ma14247506 ◽

2021 ◽

Vol 14 (24) ◽

pp. 7506

Author(s):

Boris B. Straumal ◽

Anna Korneva ◽

Gabriel A. Lopez ◽

Alexei Kuzmin ◽

Eugen Rabkin ◽

...

Keyword(s):

Liquid Phase ◽

Grain Boundary ◽

Solid Phase ◽

High Entropy Alloys ◽

Grain Boundary Engineering ◽

Phase Form ◽

High Entropy ◽

The Matrix ◽

Tie Lines ◽

Grain Boundary Wetting

In this review, the phenomenon of grain boundary (GB) wetting by the second solid phase is analyzed for the high entropy alloys (HEAs). Similar to the GB wetting by the liquid phase, the GB wetting by the second solid phase can be incomplete (partial) or complete. In the former case, the second solid phase forms in the GB of a matrix, the chain of (usually lenticular) precipitates with a certain non-zero contact angle. In the latter case, it forms in the GB continuous layers between matrix grains which completely separate the matrix crystallites. The GB wetting by the second solid phase can be observed in HEAs produced by all solidification-based technologies. The particle chains or continuous layers of a second solid phase form in GBs also without the mediation of a liquid phase, for example by solid-phase sintering or coatings deposition. To describe the GB wetting by the second solid phase, the new GB tie-lines should be considered in the two- or multiphase areas in the multicomponent phase diagrams for HEAs. The GB wetting by the second solid phase can be used to improve the properties of HEAs by applying the so-called grain boundary engineering methods.

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Grain Boundary Wetting Phenomena in High Entropy Alloys Containing Nitrides, Carbides, Borides, Silicides, and Hydrogen: A Review

Crystals ◽

10.3390/cryst11121540 ◽

2021 ◽

Vol 11 (12) ◽

pp. 1540

Author(s):

Boris Straumal ◽

Eugen Rabkin ◽

Gabriel A. Lopez ◽

Anna Korneva ◽

Alexei Kuzmin ◽

...

Keyword(s):

Grain Boundary ◽

Chemical Engineering ◽

Solid Phase ◽

Second Phase ◽

High Entropy Alloys ◽

High Entropy ◽

The Matrix ◽

Tie Lines ◽

Grain Boundary Wetting ◽

A Chain

In this review, we analyze the structure of multicomponent alloys without principal components (they are also called high entropy alloys—HEAs), containing not only metals but also hydrogen, nitrogen, carbon, boron, or silicon. In particular, we discuss the phenomenon of grain boundary (GB) wetting by the melt or solid phase. The GB wetting can be complete or incomplete (partial). In the former case, the grains of the matrix are completely separated by the continuous layer of the second phase (solid or liquid). In the latter case of partial GB wetting, the second solid phase forms, between the matrix grains, a chain of (usually lenticular) precipitates or droplets with a non-zero value of the contact angle. To deal with the morphology of GBs, the new GB tie-lines are used, which can be constructed in the two- or multiphase areas of the multidimensional HEAs phase diagrams. The GBs in HEAs in the case of complete or partial wetting can also contain hydrides, nitrides, carbides, borides, or silicides. Thus, GB wetting by the hydrides, nitrides, carbides, borides, or silicides can be used in the so-called grain boundary chemical engineering in order to improve the properties of respective HEAs.

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Microstructure and Properties of Alloys with Equal Atomic Principal Components

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.765-767.3143 ◽

2013 ◽

Vol 765-767 ◽

pp. 3143-3146

Author(s):

Yan Ping Wang ◽

Yu Zhuang ◽

Jian Chen Li

Keyword(s):

Solid Solution ◽

Principal Components ◽

Argon Atmosphere ◽

Second Phase ◽

High Entropy Alloys ◽

Arc Furnace ◽

Phase Precipitation ◽

High Entropy ◽

Bcc Structure ◽

Fcc Structure

Four high-entropy alloys are prepared by an arc furnace under argon atmosphere. The microstructure and the properties of the alloys are investigated. The results show that NiCrCuCoFe alloy consists of a single FCC solid solution. When Al presents in the alloys, the microstructures of the alloys change to a BCC+ FCC solid solution. It is indicated that Al element promotes the formation of BCC solid solution, and Si and Mn promote the formation of complicated compounds. The hardness of alloys with BCC structure is higher than that of the alloys with FCC structure. The complicated compounds are formed, the hardness increases further. The highest hardness of the alloys reaches 882 HV due to the strengthening of the second phase precipitation.

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Liquid Phase Separation in Ag-Co-Cr-Fe-Mn-Ni, Co Cr-Cu-Fe-Mn-Ni and Co-Cr-Cu-Fe-Mn-Ni-B High Entropy Alloys for Biomedical Application

Crystals ◽

10.3390/cryst10060527 ◽

2020 ◽

Vol 10 (6) ◽

pp. 527 ◽

Cited By ~ 1

Author(s):

Takeshi Nagase ◽

Mitsuharu Todai ◽

Takayoshi Nakano

Keyword(s):

Phase Separation ◽

Liquid Phase ◽

Biomedical Application ◽

Melting Process ◽

Liquid Phase Separation ◽

Heat Of Mixing ◽

High Entropy Alloys ◽

High Entropy ◽

Metallic Biomaterials ◽

Fundamental Research

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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Further comments on grain boundary wetting in liquid phase sintered Fe-Cu alloys

Metallurgical Transactions A ◽

10.1007/bf02644306 ◽

1983 ◽

Vol 14 (4) ◽

pp. 977-978 ◽

Cited By ~ 3

Author(s):

A. N. Niemi ◽

T. H. Courtney

Keyword(s):

Liquid Phase ◽

Grain Boundary ◽

Cu Alloys ◽

Grain Boundary Wetting

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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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Low Angle Grain Boundary Dewetting in Sapphire

Microscopy and Microanalysis ◽

10.1017/s1431927600027999 ◽

2001 ◽

Vol 7 (S2) ◽

pp. 384-385

Author(s):

B.J. Hockey ◽

M-K. Kang ◽

S.M. Wiederhorn ◽

J.E. Blendell

Keyword(s):

Liquid Phase ◽

Grain Boundary ◽

Liquid Phase Sintering ◽

Sintering Process ◽

Transmission Electron ◽

Wide Range ◽

Grain Boundary Wetting ◽

Tape Cast ◽

Single Boundary ◽

Current Emphasis

The structure and composition of low angle grain boundaries produced in sapphire by a liquid phase sintering process were investigated by conventional and high resolution transmission electron microscopy (CTEM and HRTEM, respectively). Considering the current emphasis on producing ceramics with textured microstructures for various applications, the question of grain boundary wetting vs. dewetting has become a relevant issue to determining the microstructure development and the properties of these liquid phase sintered materials. Accordingly, the present study was designed to cover a wide range of tilt misorientations, twist misorientations, and boundary orientations.The boundaries were formed by the directed growth of two sapphire plates, both having nominal <0001>, , or surface orientations through an alumina tape-cast containing an anorthite composition glass phase. After an initial hot-pressing stage, followed by an anneal at 1600° C for 200 hours, the samples typically contained a single boundary delineated by isolated pockets of entrapped glass, Fig. 1.

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Effect of the Annealing Treatment on the Microstructure, Microhardness and Corrosion Behaviour of Al0.3CrFe1.5MnNi0.5 High-Entropy Alloys

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.748.79 ◽

2013 ◽

Vol 748 ◽

pp. 79-85 ◽

Cited By ~ 2

Author(s):

L.C. Tsao ◽

C.S. Chen ◽

Kuo Huan Fan ◽

Yen Teng Huang

Keyword(s):

Corrosion Behaviour ◽

Dendritic Structure ◽

Annealing Treatment ◽

Age Hardening ◽

High Entropy Alloy ◽

Second Phase ◽

High Entropy Alloys ◽

High Entropy ◽

Fcc Phase ◽

Bcc Phase

In this study, an Al0.3CrFe1.5MnNi0.5high entropy alloy was synthesized by arc-melting in Ar. The as-cast alloy ingot was heat treated for 8 h at 650-750°C and then cooled in furnace to investigate the effects of age treatment on the microstructure, hardness and corrosion behaviour. The microstructure of as-cast sample has a typical rich-Cr BCC structure of dendrites, rich-Ni FCC interdendrite phases and a small fraction of cross-like rich-Ni FCC phase within the majority dendritic structure. During annealing treatment at 650°C, the cross-like FCC phase (β-FCC) gradually decreased, dendritic rich-Cr BCC phase transfers to Cr5Fe6Mn8phase, and the AlNi phase precipitated within the matrix dendrites. The interdendritic β1-FCC phases gradually decomposed and transfers to second-phase (β2FCC), and the AlNi precipitated phase coarsen during annealing at 750°C. In addition, Cr5Fe6Mn8phase gradually transfers to rich-Cr BCC phase during slow-cooling process. These precipitation phases in the grain matrix are the main age hardening mechanism. The potentiodynamic polarization of the Al0.3CrFe1.5MnNi0.5high entropy alloys, obtained in 3.5% NaCl solutions, clearly revealed that the corrosion resistance increases and the passive region decreases as annealing temperature increasing.

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Effects of Y, GdCu, and Al Addition on the Thermoelectric Behavior of CoCrFeNi High Entropy Alloys

Metals ◽

10.3390/met8100781 ◽

2018 ◽

Vol 8 (10) ◽

pp. 781 ◽

Cited By ~ 2

Author(s):

Wanqing Dong ◽

Zheng Zhou ◽

Lijun Zhang ◽

Mengdi Zhang ◽

Peter Liaw ◽

...

Keyword(s):

Thermoelectric Properties ◽

Thermoelectric Materials ◽

Alternative Energy ◽

Phonon Scattering ◽

Waste Heat ◽

Second Phase ◽

High Entropy Alloys ◽

High Entropy ◽

Alternative Energy Sources ◽

The Future

Thermoelectric (TE) materials can interconvert waste heat into electricity, which will become alternative energy sources in the future. The high-entropy alloys (HEAs) as a new class of materials are well-known for some excellent properties, such as high friction toughness, excellent fatigue resistance, and corrosion resistance. Here, we present a series of HEAs to be potential candidates for the thermoelectric materials. The thermoelectric properties of YxCoCrFeNi, GdxCoCrFeNiCu, and annealed Al0.3CoCrFeNi were investigated. The effects of grain size and formation of the second phase on thermoelectric properties were revealed. In HEAs, we can reduce the thermal conductivity by controlling the phonon scattering due to the considerable complexity of the alloys. The Y, Gd-doped HEAs are competitive candidate thermoelectric materials for energy conversion in the future.

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