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Synthesis, Characterization and Applications of High-Entropy Alloys

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A special issue of Materials (ISSN 1996-1944). This special issue belongs to the section "Metals and Alloys".

Deadline for manuscript submissions: closed (20 February 2023) | Viewed by 7654

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Special Issue Editor

Dr. Shuangxi Song

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Guest Editor

School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, China
Interests: HEA; metallic glasses; metastable materials, mechanical behavior; microstructure characterization

Special Issue Information

Dear Colleagues,

High-entropy alloys (HEAs) are a lass of new multicomponent alloys with five or more components in equal or near-equal concentrations and have been investigated extensively since they were first described in 2004. Unlike conventional alloys that are normally based on a single host metal, the high entropy of mixing and disordered solution of several elements in HEAs competes with the enthalpy of phase formation. As a result, either single- or multi-phase HEAs can be produced. Based on the type of elements and configurational entropy, several categories have emerged: transition-metal-based HEAs, refractory HEAs, low-density HEAs, ceramic HEAs, and their derivatives, such as medium-entropy alloys (MEAs) with 2–4 principal elements.

Resulting from the multi-element environment, slower diffusion rates, high friction forces on dislocations, and the propensity for twinning contribute to the excellent mechanical properties in HEAs—for example, a continuous work-hardening rate that is sustained to large plastic strains (~0.5) and outstandingly high fracture toughness values. The resistance to shear-band formation under dynamic loading greatly enhance the ballistic properties in HEAs. These extraordinary mechanical properties and ease of processing by conventional means suggest significant applications in many future structural materials.

The aim of this SI is to comprehensively understand the latest developments on the synthesis, characterization, and application of multicomponent HEAs. It is my pleasure to invite you to submit manuscripts on the subject of HEAs for this Special Issue. Full papers, communications, and reviews are all welcome.

Dr. Shuangxi Song
Guest Editor

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. Materials is an international peer-reviewed open access semimonthly 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
characterization
microstructure
mechanical properties
thermodynamic properties
thin films
nanoparticles
melting and casting
mechanical alloying and milling
additive manufacturing

Published Papers (3 papers)

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Research

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21 pages, 5462 KiB

Open AccessArticle

Microstructure-Property Correlation and Its Evolution during Aging in an Al_4.4Co₂₆Cr₁₉Fe₁₈Ni₂₇Ti_5.6 High-Entropy Alloy

by Florian Biermair, Francisca Mendez-Martin, Vsevolod I. Razumovskiy, Franco Moitzi and Gerald Ressel

Materials 2023, 16(7), 2821; https://doi.org/10.3390/ma16072821 - 1 Apr 2023

Cited by 2 | Viewed by 1155

Abstract

The efficient energy use in multiple sectors of modern industry is partly based on the efficient use of high-strength, high-performance alloys that retain remarkable mechanical properties at elevated and high temperatures. High-entropy alloys (HEAs) represent the most recent class of these materials with a high potential for high-temperature high-strength applications. Aside from their chemical composition and microstructure-property relationship, limited information on the effect of heat treatment as a decisive factor for alloy design is available in the literature. This work intends to contribute to this research topic by investigating the effect of heat treatment on the microstructure and mechanical performance of an Al_4.4Co₂₆Cr₁₉Fe₁₈Ni₂₇Ti_5.6 HEA. The solution annealed state is compared to aged states obtained at different heat treatment times at 750 °C. The temporal evolution of the matrix and the γ’-precipitates are analyzed in terms of chemical composition, crystallography, size, shape, and volume fraction by means of scanning electron microscopy, transmission electron microscopy, and atom probe tomography. The yield strength evolution and strength contributions are calculated by classical state-of-the-art models as well as by ab-initio-based calculations of the critical resolved shear stress. The findings indicate promising mechanical properties of the investigated alloy and provide insight not only into possible strengthening mechanisms but also into the evolution of main phases during the heat treatment. Full article

(This article belongs to the Special Issue Synthesis, Characterization and Applications of High-Entropy Alloys)

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15 pages, 16138 KiB

Open AccessArticle

Synthesis of Refractory High-Entropy Alloy WTaMoNbV by Powder Bed Fusion Process Using Mixed Elemental Alloying Powder

by Tomer Ron, Avi Leon, Vladimir Popov, Evgeny Strokin, Dan Eliezer, Amnon Shirizly and Eli Aghion

Materials 2022, 15(12), 4043; https://doi.org/10.3390/ma15124043 - 7 Jun 2022

Cited by 17 | Viewed by 2263

Abstract

The growing interest in refractory high-entropy alloys (HEAs) in the last decade is mainly due to their thermal stability, outstanding mechanical properties, and excellent corrosion resistance. However, currently HEAs are still not considered for use as common structural materials due to their inherent drawbacks in terms of processing and machining operations. The recent progress witnessed in additive manufacturing (AM) technologies has raised the option of producing complex components made of HEAs with minimal machining processes. So far, this could be achieved by using pre-alloyed powders of HEAs that were mainly produced by a conventional arc melting furnace (AMF) in the form of small compounds that were transformed into powder via a gas atomization process. To significantly reduce the production cost, the present study aims to analyze the ability to synthesize HEA WTaMoNbV via a laser powder bed fusion (LPBF) process using mixed elemental alloying powder as the raw material. For comparison, a counterpart alloy with the same chemical composition was analyzed and produced by an AMF process. The microstructures of the tested alloys were examined by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD) analyses. The physical properties were evaluated in terms of density and mechanical strength, while the electrochemical behavior was assessed by potentiodynamic polarization analysis. The results disclosed similarities in microstructure, physical properties and electrochemical behavior between HEA WTaMoNbV manufactured by the proposed LPBF process and its counterpart alloy produced by an AMF process. Full article

(This article belongs to the Special Issue Synthesis, Characterization and Applications of High-Entropy Alloys)

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Review

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19 pages, 9363 KiB

Open AccessReview

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

by Boris B. Straumal, Anna Korneva, Gabriel A. Lopez, Alexei Kuzmin, Eugen Rabkin, Gregory Gerstein, Alexander B. Straumal and Alena S. Gornakova

Materials 2021, 14(24), 7506; https://doi.org/10.3390/ma14247506 - 7 Dec 2021

Cited by 25 | Viewed by 2711

Abstract

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. Full article

(This article belongs to the Special Issue Synthesis, Characterization and Applications of High-Entropy Alloys)

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