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Crystals
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High-Entropy Materials
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High-Entropy Materials

A special issue of Crystals (ISSN 2073-4352). This special issue belongs to the section "Crystalline Metals and Alloys".

Deadline for manuscript submissions: closed (20 December 2021) | Viewed by 18167

Special Issue Editors

Dr. Rui Feng

E-Mail Website
Guest Editor
Oak Ridge National Laboratory, Oak Ridge, TN 37830, USA
Interests: high-entropy alloys; alloy design; microstructural characterization; mechanical behavior; neutron scattering
Dr. Ke An

E-Mail Website
Guest Editor
Oak Ridge National Laboratory, Oak Ridge, TN 37830, USA
Interests: neutron scattering; deformation; phase transformation
Special Issues, Collections and Topics in MDPI journals
Prof. Peter K. Liaw

grade E-Mail Website
Guest Editor
Department of Materials Science and Engineering, University of Tennessee, Knoxville, TN 37996-2100, USA
Interests: mechanical behavior; fatigue and fracture behavior; nondestructive evaluation; neutron/synchrotron studies of advanced materials, including bulk metallic glasses; nanostructural materials; high-entropy alloys; superalloys; steels; intermetallics
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

High-entropy alloys, also referred to as multi-principal alloys or compositionally-complex alloys, are attracting extensive attention from materials scientists because of their exceptional properties, such as high strength, excellent ductility, exceptional fatigue and fracture resistance, and great corrosion resistance. The concept of HEAs has revolutionized traditional alloy design using multi-principal components instead of one or two base elements, which create endless composition space to design high-performance materials. Inspired by the HEA concept in metal alloys, the idea of using multi-principal components has also been extended to other types of materials for pursuing promising properties, such as high-entropy oxides, high-entropy nitrides, high-entropy carbides, etc. The rapid development of various high-entropy materials is pushing people to develop new synthesis and characterization techniques and to have fundamental understandings of their processing-microstructure–property relationships that may be different from those of conventional materials. This Special Issue on High-Entropy Materials will offer a dedicated platform for sharing new findings and communicating views in high-entropy materials, so that scientific understanding and future applications of the high-entropy materials can be accelerated. The specific topics of interest include (but are not limited to) high-entropy alloys/ceramics/composites, materials design, synthesis and processing, microstructures and properties, modeling and simulation, machine learning, and high-throughput methods.

Dr. Rui Feng
Dr. Ke An
Prof. Dr. Peter K. Liaw
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Crystals is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • high-entropy alloys/ceramics/composites
  • alloy design
  • synthesis and processing
  • microstructure
  • properties
  • deformation mechanism
  • theoretical calculations
  • machine learning and high-throughput methods

Published Papers (7 papers)

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Research

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12 pages, 2631 KiB  
Article
Mechanical Behavior and Thermal Stability of (AlCrTiZrMo)N/ZrO2 Nano-Multilayered High-Entropy Alloy Film Prepared by Magnetron Sputtering
by Qingqing Zhai, Wei Li, Ping Liu, Wenjie Cheng, Ke Zhang, Fengcang Ma, Xiaohong Chen, Rui Feng and Peter K. Liaw
Crystals 2022, 12(2), 232; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst12020232 - 08 Feb 2022
Cited by 4 | Viewed by 1365
Abstract
A new type of high-entropy alloy, a nitride-based (AlCrTiZrMo)N/ZrO2 nano-multilayered film, was designed to investigate the effect of ZrO2 layer thickness on the microstructure, mechanical properties, and thermal stability. The results show that when the thickness of the ZrO2 layer [...] Read more.
A new type of high-entropy alloy, a nitride-based (AlCrTiZrMo)N/ZrO2 nano-multilayered film, was designed to investigate the effect of ZrO2 layer thickness on the microstructure, mechanical properties, and thermal stability. The results show that when the thickness of the ZrO2 layer is less than 0.6 nm, it can be transformed into cubic-phase growth under the template effect of the (AlCrTiZrMo)N layer, resulting in an increased hardness. The (AlCrTiZrMo)N/ZrO2 film with a ZrO2 layer thickness of 0.6 nm has the highest hardness and elastic modulus of 35.1 GPa and 376.4 GPa, respectively. As the thickness of the ZrO2 layer further increases, ZrO2 cannot maintain the cubic structure, and the epitaxial growth interface is destroyed, resulting in a decrease in hardness. High-temperature annealing treatments indicate that the mechanical properties of the film decrease slightly after annealing at less than 900 °C for 30 min, while the mechanical properties decrease significantly after annealing for 30 min at 1000–1100 °C. The hardness and elastic modulus after annealing at 900 °C are still 24.5 GPa and 262.3 GPa, showing excellent thermal stability. This conclusion verifies the “template” effect of the nano-multilayered film, which improves the hardness and thermal stability of the high-entropy alloy. Full article
(This article belongs to the Special Issue High-Entropy Materials)
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10 pages, 3018 KiB  
Article
Improvement of Mechanical Properties with Non-Equimolar CrNbTaVW High Entropy Alloy
by Francisco Antão, Ricardo Martins, José Brito Correia, Rui Coelho da Silva, António Pereira Gonçalves, Elena Tejado, José Ygnacio Pastor, Eduardo Alves and Marta Dias
Crystals 2022, 12(2), 219; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst12020219 - 01 Feb 2022
Cited by 4 | Viewed by 1633
Abstract
CrNbTaVWx with (x = 1 and 1.7) high entropy alloys have been devised for thermal barriers between the plasma-facing tungsten tiles and the copper-based heat sink in the first wall of fusion nuclear reactors. These novel materials were prepared by ball milling [...] Read more.
CrNbTaVWx with (x = 1 and 1.7) high entropy alloys have been devised for thermal barriers between the plasma-facing tungsten tiles and the copper-based heat sink in the first wall of fusion nuclear reactors. These novel materials were prepared by ball milling and consolidated by Upgrade Field Assisted Sintering Technology at 1873 K under an applied pressure of 90 MPa for 10 min. In this work, the structural and mechanical properties of these materials were evaluated. Consolidated samples presented a major phase with a bcc-type structure with lattice parameter value of 0.316 nm for CrNbTaVW and CrNbTaVW1.7 compositions. Moreover, observation of the microstructures evidences also two minor phases: Ta-Nb-Cr and Ta-V rich (in which carbon is detected). Despite the similarity in the structural properties of these two alloys, their mechanical properties are distinct. The flexural stress for the sample with higher amount of W (CrNbTaVW1.7) is higher by 50% in the 298–873 K range, with an increased strain to fracture, which can be associated with reduced brittleness caused by the additional W incorporation. Full article
(This article belongs to the Special Issue High-Entropy Materials)
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9 pages, 1185 KiB  
Article
Tensile Response of As-Cast CoCrFeNi and CoCrFeMnNi High-Entropy Alloys
by Tu-Ngoc Lam, Mao-Yuan Luo, Takuro Kawasaki, Stefanus Harjo, Jayant Jain, Soo-Yeol Lee, An-Chou Yeh and E-Wen Huang
Crystals 2022, 12(2), 157; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst12020157 - 21 Jan 2022
Cited by 9 | Viewed by 3076
Abstract
In this research, we systematically investigated equiatomic CoCrFeNi and CoCrFeMnNi high-entropy alloys (HEAs). Both of these HEA systems are single-phase, face-centered-cubic (FCC) structures. Specifically, we examined the tensile response in as-cast quaternary CoCrFeNi and quinary CoCrFeMnNi HEAs at room temperature. Compared to CoCrFeNi [...] Read more.
In this research, we systematically investigated equiatomic CoCrFeNi and CoCrFeMnNi high-entropy alloys (HEAs). Both of these HEA systems are single-phase, face-centered-cubic (FCC) structures. Specifically, we examined the tensile response in as-cast quaternary CoCrFeNi and quinary CoCrFeMnNi HEAs at room temperature. Compared to CoCrFeNi HEA, the elongation of CoCrFeMnNi HEA was 14% lower, but the yield strength and ultimate tensile strength were increased by 17% and 6%, respectively. The direct real-time evolution of structural defects during uniaxial straining was acquired via in situ neutron-diffraction measurements. The dominant microstructures underlying plastic deformation mechanisms at each deformation stage in as-cast CoCrFeNi and CoCrFeMnNi HEAs were revealed using the Convolutional Multiple Whole Profile (CMWP) software for peak-profile fitting. The possible mechanisms are reported. Full article
(This article belongs to the Special Issue High-Entropy Materials)
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7 pages, 1805 KiB  
Article
Corrosion Behavior of Cr19Fe22Co21Ni25Mo13 Alloy in 1M Nitric Acid and 1M Hydrochloric Acid Solutions
by Chun-Huei Tsau and Po-Min Chen
Crystals 2021, 11(11), 1289; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst11111289 - 25 Oct 2021
Cited by 2 | Viewed by 1430
Abstract
The present work studied the microstructures of Cr19Fe22Co21Ni25Mo13 alloy, and tested the polarization properties in deaerated 1M nitric acid and 1M hydrochloric solutions at different temperatures. The alloy was processed by an argon atmosphere [...] Read more.
The present work studied the microstructures of Cr19Fe22Co21Ni25Mo13 alloy, and tested the polarization properties in deaerated 1M nitric acid and 1M hydrochloric solutions at different temperatures. The alloy was processed by an argon atmosphere arc-melting. Results indicated that the microstructure of Cr19Fe22Co21Ni25Mo13 alloy was a dendritic one. The dendrites of Cr19Fe22Co21Ni25Mo13 alloy were an FCC structure, and the interdendrites of Cr19Fe22Co21Ni25Mo13 alloy were a eutectic structure with two phases of FCC and simple cubic (SC). The Cr19Fe22Co21Ni25Mo13 alloy had better corrosion resistance compared with commercial 304 stainless steel in both deaerated 1M HNO3 and 1M HCl solutions. The corrosion types of Cr19Fe22Co21Ni25Mo13 alloy in both of 1M HNO3 and 1M HCl solutions were uniform corrosion. Full article
(This article belongs to the Special Issue High-Entropy Materials)
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11 pages, 3335 KiB  
Article
Microstructures and Mechanical Properties of Al-Ti-Zr-Nb-Ta-Mo-V Refractory High-Entropy Alloys with Coherent B2 Nanoprecipitation
by Zhenhua Wang, Dongming Jin, Jincan Han, Qing Wang, Zhongwei Zhang and Chuang Dong
Crystals 2021, 11(7), 833; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst11070833 - 19 Jul 2021
Cited by 7 | Viewed by 3123
Abstract
In this work, the microstructural evolution and mechanical properties of new body-centered cubic (BCC)-based Al-Ti-Zr-Nb-Ta-Mo-V refractory high-entropy alloys (RHEAs) with coherent B2 precipitation are investigated. These designed alloy ingots were solid-solutionized at 1573 K for 2 h and then aged at 873 K [...] Read more.
In this work, the microstructural evolution and mechanical properties of new body-centered cubic (BCC)-based Al-Ti-Zr-Nb-Ta-Mo-V refractory high-entropy alloys (RHEAs) with coherent B2 precipitation are investigated. These designed alloy ingots were solid-solutionized at 1573 K for 2 h and then aged at 873 K for 24 h, in which each treatment was followed by water quenching. It was found that there exists phase separation of BCC matrix, Ti/Zr-rich BCC1 and Nb/Ta-rich BCC2 in these alloys. Moreover, ultra-fine spherical B2 nanoparticles with a size of 3~5 nm were dispersed in BCC2 matrix. These B2 nanoparticles could be coarsened up to 25~50 nm after aging and the particle morphology also changes to a cuboidal shape due to a moderate lattice misfit (ε = 0.7~2.0%). Also, Zr5Al3 phase could coexist with the B2 phase, where the difference between them is that the Ti element is enriched in B2 phase, rather than in Zr5Al3. Among them, the solutionized Al2Ti5Zr4Nb2.5Ta2.5 RHEAs exhibit good compressive mechanical property with a high yield strength of 1240 MPa and a large plasticity, which is mainly attributed to the coherent precipitation in the BCC matrix. Full article
(This article belongs to the Special Issue High-Entropy Materials)
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Review

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21 pages, 3320 KiB  
Review
Recent Progress on High-Entropy Films Deposited by Magnetron Sputtering
by Mohamed El Garah, Pascal Briois and Frederic Sanchette
Crystals 2022, 12(3), 335; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst12030335 - 27 Feb 2022
Cited by 12 | Viewed by 3468
Abstract
High-entropy films (HEFs) are of considerable interest in surface engineering applications due to their superior properties, such as good corrosion resistance, good thermal stability and excellent high temperature oxidation. Recently, the scientific community has seen an increasing development of the multicomponent coatings, improving [...] Read more.
High-entropy films (HEFs) are of considerable interest in surface engineering applications due to their superior properties, such as good corrosion resistance, good thermal stability and excellent high temperature oxidation. Recently, the scientific community has seen an increasing development of the multicomponent coatings, improving their properties compared to conventional films. Technically, different strategies have been exploited to fabricate HEFs. Magnetron-sputtered HEFs have made significant advancements in this field. HEFs have various applications given their interesting performances. This article overviews the development and the outcome of HEFs prepared using the magnetron sputtering technique. The classification of HEFs is reported. The effect of magnetron sputtering parameters on the microstructural, mechanical, electrochemical and thermal properties of HEFs is also discussed. Applications of HEFs are reported in the last section. Full article
(This article belongs to the Special Issue High-Entropy Materials)
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18 pages, 47218 KiB  
Review
Grain Boundary Wetting Phenomena in High Entropy Alloys Containing Nitrides, Carbides, Borides, Silicides, and Hydrogen: A Review
by Boris Straumal, Eugen Rabkin, Gabriel A. Lopez, Anna Korneva, Alexei Kuzmin, Alena Gornakova, Alexander Straumal and Brigitte Baretzky
Crystals 2021, 11(12), 1540; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst11121540 - 09 Dec 2021
Cited by 13 | Viewed by 2967
Abstract
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 [...] Read more.
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. Full article
(This article belongs to the Special Issue High-Entropy Materials)
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