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High Entropy Alloy Films
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High Entropy Alloy Films

A special issue of Coatings (ISSN 2079-6412). This special issue belongs to the section "Thin Films".

Deadline for manuscript submissions: 20 May 2024 | Viewed by 9959

Special Issue Editor

Prof. Dr. Chun-Hway Hsueh

E-Mail Website
Guest Editor
Department of Materials Science and Engineering, National Taiwan University, Taipei 10617, Taiwan
Interests: thermomechanical properties; thin films; metallic glasses; high entropy alloys; nanoindentation; surface-enhanced Raman scattering; plasmonics nanodevices

Special Issue Information

Dear Colleagues,

The concept of high entropy alloys (HEAs) was first proposed by Yeh et al. and Cantor et al. in 2004. Unlike the traditional alloys with one or rarely two base elements, HEAs contain at least five principal elements. Because of the synergy of high-entropy effects, severe lattice distortion, and sluggish diffusion, HEAs can form simple solid-solutions instead of intermetallic compounds. Extensive studies have been performed on various HEAs and many attractive properties have been achieved, such as high hardness and strength, high fatigue resistance, high corrosion resistance, high-temperature oxidation resistance, excellent biocompatibility, and enhanced irradiation resistance, etc., which have potential for structural and functional applications. At present, most of the HEAs have been fabricated by arc melting and casting. In recent years, a counterpart of the HEA, the HEA film (HEAF), has been developed. Different technologies have been adopted to fabricate HEAFs, including sputtering, electrodeposition, spraying, laser cladding, and plasma-transferred arc cladding, etc. Compared to HEAs, HEAFs experience a much faster cooling rate during the fabrication process which, in turn, would restrict the diffusion of elements and the formation of intermetallic compounds. As a result, HEAFs possess different structures and properties compared with their bulk counterparts. Experimental results have also shown the excellent mechanical and physical properties of HEAFs. This Special Issue, entitled “High Entropy Alloy Films” addresses the current understandings, new development, and challenges in a wide range of topics on HEAFs. The aim of this Special Issue is to provide a platform to bring together high-quality research and innovative ideas, and to bridge the gap between the fundamental research and applications for HEAFs. In particular, the topics of interest include, but are not limited to:

  • Thin film technologies
  • Composition design
  • Structures and properties
  • Hardening and strengthening
  • Modeling
  • Applications

Prof. Dr. Chun-Hway Hsueh
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. Coatings 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 alloy films
  • Thin film technologies
  • Composition design
  • Structures and properties
  • Hardening and strengthening
  • Modeling
  • Applications

Published Papers (6 papers)

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Research

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17 pages, 8502 KiB  
Article
The Influence of Nitrogen Partial Pressure on the Microstructure and Mechanical Properties of HfNbTaTiVZr High-Entropy Nitride Coating Deposited via Direct Current Cathodic Vacuum Arc Deposition
by Tim Krülle, Martin Kuczyk, Michael Leonhardt, Otmar Zimmer and Christoph Leyens
Coatings 2024, 14(4), 398; https://doi.org/10.3390/coatings14040398 - 28 Mar 2024
Viewed by 537
Abstract
In recent years, high-entropy alloys have attracted increasing scientific interest. Due to their promising combination of properties, such as high hardness and high temperature stability, they are attractive for use as tool coatings for machining applications, to give but one example. Previous studies [...] Read more.
In recent years, high-entropy alloys have attracted increasing scientific interest. Due to their promising combination of properties, such as high hardness and high temperature stability, they are attractive for use as tool coatings for machining applications, to give but one example. Previous studies often focused on layer deposition using magnetron sputtering. Comparatively little research has been carried out to date on coating deposition using direct current cathodic vacuum arc deposition (CAE), with higher achievable rates and almost completely ionized plasmas. The aim of this work is to investigate (HfNbTaTiZr)N-coatings produced by CAE. The nitrogen content was varied and the effects on the coating properties were investigated. Changing the N2/(N2 + Ar) ratio between 0.1 and 1.0 and varying the working pressure in the chamber from 2 Pa to 5 Pa resulted in variations of the nitrogen content of the coatings, ranging from 30 at% to 50 at%. Although different microstructures of the coatings were obtained, there was only a minor influence on the hardness and Young’s modulus. Full article
(This article belongs to the Special Issue High Entropy Alloy Films)
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17 pages, 13507 KiB  
Article
Mechanical Properties and Corrosion Resistance of AlCrNbSiTiN High Entropy Alloy Nitride Coatings
by Bih-Show Lou, Yu-Chen Lin and Jyh-Wei Lee
Coatings 2023, 13(10), 1724; https://doi.org/10.3390/coatings13101724 - 02 Oct 2023
Cited by 3 | Viewed by 992
Abstract
High-entropy alloy (HEA) nitride coatings have been extensively studied due to their desirable properties of high hardness, thermal stability, and corrosion resistance. Among HEA nitride thin films, the AlCrNbSiTiN coatings exhibit very good hardness, high temperature strength, and thermal stability. In this study, [...] Read more.
High-entropy alloy (HEA) nitride coatings have been extensively studied due to their desirable properties of high hardness, thermal stability, and corrosion resistance. Among HEA nitride thin films, the AlCrNbSiTiN coatings exhibit very good hardness, high temperature strength, and thermal stability. In this study, six AlCrNbSiTiN HEA coatings with different Al and Cr contents were synthesized using a co-sputtering system with a high-power impulse magnetron sputtering (HiPIMS) power connected to an Al70Cr30 target and a mid-frequency power connected with an Al4Cr2NbSiTi2 high-entropy alloy target. The input power of the Al70Cr30 target was adjusted to obtain AlCrNbSiTiN coatings with different Al and Cr contents. It is observed that the sum of the Al and Cr contents and the (Al + Cr)/(Al + Cr + Nb + Si + Ti) ratio of the AlCrNbSiTiN coatings increased from 59 to 91 at.% when the input power of the Al70Cr30 target increased from 700 W to 1100 W. The single NaCl-type (B1) face-centered cubic (FCC) phase was observed for each coating. The hardness of the coatings increased from 21.2 to 28.2 GPa with increasing Al and Cr contents due to the grain size refinement effect brought by the increasing HiPIMS power. The wear depth and wear rate of the coatings sequentially decreased from 544 to 24 nm and from 2.79 × 10−5 to 2.63 × 10−7 mm3N−1m−1, respectively. Although the adhesion slowly decreased with increasing Al and Cr contents and the hardness of the coating, there was adequate adhesion with a minimum LC3 critical load of 36.1 N. The corrosion resistance of 304 stainless steel in a 3.5 wt.% NaCl aqueous solution was improved by deposition of the AlCrNbSiTiN coating. In this work, the high-entropy AlCrNbSiTiN nitride coating with a (Al + Cr)/(Al + Cr + Nb + Si + Ti) ratio of 91% exhibited excellent surface roughness, the highest hardness of 28.2 GPa, adequate adhesion, and the lowest wear rate of 2.63 × 10−7 mm3N−1m−1 due to its grain refinement effect by the ion bombardment generated with HiPIMS. Full article
(This article belongs to the Special Issue High Entropy Alloy Films)
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10 pages, 6140 KiB  
Article
High-Throughput Preparation and Mechanical Property Screening of Zr-Ti-Nb-Ta Multi-Principal Element Alloys via Multi-Target Sputtering
by Haochen Qiu, Xuehui Yan, Shuaishuai Wu, Wei Jiang, Baohong Zhu and Shengli Guo
Coatings 2023, 13(9), 1650; https://doi.org/10.3390/coatings13091650 - 20 Sep 2023
Viewed by 652
Abstract
Zr-Ti-Nb-Ta alloys were synthesized in parallel via multi-target co-sputtering deposition with physical masking in a pseudo-ternary Ti-Nb-ZrTa alloy system. Sixteen alloys with distinct compositions were obtained. Comprehensive characterization of phase structure, microstructure, Young’s modulus, and nanoindentation hardness was undertaken. The Ti-Nb-ZrTa alloys exhibited [...] Read more.
Zr-Ti-Nb-Ta alloys were synthesized in parallel via multi-target co-sputtering deposition with physical masking in a pseudo-ternary Ti-Nb-ZrTa alloy system. Sixteen alloys with distinct compositions were obtained. Comprehensive characterization of phase structure, microstructure, Young’s modulus, and nanoindentation hardness was undertaken. The Ti-Nb-ZrTa alloys exhibited two typical phase structures: a single-BCC solid-solution structure, and an amorphous structure. Nanoindentation quantification confirmed a Young’s modulus ranging from 110 to 130 GPa, alongside nanoindentation hardness spanning 3.6 to 5.0 GPa. The combination of good hardness and a relatively low Young’s modulus renders these alloys promising candidates for excellent biomedical materials. This work not only offers an effective method for the high-throughput synthesis of multi-principal element alloys, but also sheds light on a strategy for screening the phase structure and mechanical performance within a given alloy system. Full article
(This article belongs to the Special Issue High Entropy Alloy Films)
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10 pages, 3180 KiB  
Article
Macroparticle Reduction and Its Transport Mechanism through a Magnetic Filter during Cathodic Vacuum Arc Deposition with an HEA Target
by Pei-En Lee, Yu-Kuan Tu, Ming-Hung Tsai, Che-Wei Tsai and Jien-Wei Yeh
Coatings 2022, 12(10), 1437; https://doi.org/10.3390/coatings12101437 - 29 Sep 2022
Viewed by 1283
Abstract
By cathodic arc deposition, the effects of the magnetic field, working pressure, inner-wall structure, and cross-section area of the magnetic-filter duct on the macroparticle (MP) distribution were investigated with a high-entropy alloy target. The MP density increased with the density of the plasma [...] Read more.
By cathodic arc deposition, the effects of the magnetic field, working pressure, inner-wall structure, and cross-section area of the magnetic-filter duct on the macroparticle (MP) distribution were investigated with a high-entropy alloy target. The MP density increased with the density of the plasma beam transporting through the filter duct, which was increased by the magnetic field or working pressure. In order to reduce the MP density, equally spaced circumferential Cu-sheet baffle and lining of 304-stainless-steel wire mesh were used as the inner-wall structure, respectively, but the improvement was limited. However, inserting an Al foil disk with a round opening for the passage of the main plasma stream at the bend position of the duct remarkably reduced the area fraction of the MPs from 4.8% to 0.6%. These results demonstrate that the main transport mechanism of the MPs was the entrainment in the plasma beam through the duct. In addition, reducing the cross section of the filter duct was suggested to be an effective method to reduce MPs. This method could be utilized for high-MP generation targets such as high-entropy alloys. Full article
(This article belongs to the Special Issue High Entropy Alloy Films)
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14 pages, 1804 KiB  
Article
Effects of Nb Addition on Microstructures and Mechanical Properties of Nbx-CoCrFeMnNi High Entropy Alloy Films
by Yu-Hsuan Liang, Chia-Lin Li and Chun-Hway Hsueh
Coatings 2021, 11(12), 1539; https://doi.org/10.3390/coatings11121539 - 14 Dec 2021
Cited by 13 | Viewed by 2758
Abstract
In the present work, Nbx-CoCrFeMnNi high entropy alloy films (HEAFs, 0 to 7.2 at.% Nb) were fabricated by radio frequency (RF) magnetron co-sputtering of CoCrFeMnNi alloy and Nb targets. The effects of Nb addition on the microstructures and mechanical properties of [...] Read more.
In the present work, Nbx-CoCrFeMnNi high entropy alloy films (HEAFs, 0 to 7.2 at.% Nb) were fabricated by radio frequency (RF) magnetron co-sputtering of CoCrFeMnNi alloy and Nb targets. The effects of Nb addition on the microstructures and mechanical properties of HEAFs were systematically investigated. For Nb-free film (0 at.% Nb), the face-centered cubic (FCC) peaks were identified in the X-ray diffraction (XRD) pattern. The addition of Nb resulted in a broadening of diffraction peaks, a decrease in peak intensity, and the vanishment of high-angle peaks. Transmission electron microscope (TEM) images indicated the formation of nanotwins at low Nb concentrations, and a transition from a single phase FCC solid solution to an amorphous phase was observed with the increasing Nb concentration. The films were strengthened with an increase in Nb concentration. Specifically, the hardness characterized by nanoindentation increased from 6.5 to 8.1 GPa. The compressive yield strength and fracture strength measured from micropillar compression tests were improved from 1.08 GPs and 2.56 GPa to 2.70 GPa and 5.76 GPa, respectively, whereas the fracture strain decreased from >29.4% (no fracture) to 15.8%. Additionally, shear banding was observed in the presence of amorphous phase. Full article
(This article belongs to the Special Issue High Entropy Alloy Films)
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Review

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19 pages, 4197 KiB  
Review
High-Entropy Alloy Films
by Kaixuan Cui and Yong Zhang
Coatings 2023, 13(3), 635; https://doi.org/10.3390/coatings13030635 - 17 Mar 2023
Cited by 6 | Viewed by 2475
Abstract
High-entropy alloy films have the same excellent properties as high-entropy alloys and can better realize the practical applications of high-entropy alloys. This paper takes the high-entropy alloy films as the object of discussion. The preparation process, microstructure, hardness, wear resistance and corrosion resistance [...] Read more.
High-entropy alloy films have the same excellent properties as high-entropy alloys and can better realize the practical applications of high-entropy alloys. This paper takes the high-entropy alloy films as the object of discussion. The preparation process, microstructure, hardness, wear resistance and corrosion resistance of high-entropy alloy films are mainly discussed and the influence of nitridation, sputtering power, substrate temperature, substrate bias and other factors on the phase structure of alloy films is analyzed. High-entropy alloy films can be prepared using magnetron sputtering, laser cladding, pulsed laser deposition, detonation spraying, electrochemical deposition and other processes. High-entropy alloy films tend to form a solid solution and amorphous state, and their hardness is far higher than that of traditional films. Among them, the hardness of high-entropy alloy nitride films can reach the standard of superhard films. Wear resistance is usually proportional to hardness. Due to the corrosion-resistant elements and amorphous structure, some high-entropy alloy films have better corrosion resistance than stainless steel. High-entropy alloy films have shown profound development prospects in the fields of wear-resistant coatings for tools, corrosion protection, diffusion barrier and photothermal conversion coatings. Full article
(This article belongs to the Special Issue High Entropy Alloy Films)
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Planned Papers

The below list represents only planned manuscripts. Some of these manuscripts have not been received by the Editorial Office yet. Papers submitted to MDPI journals are subject to peer-review.

Tentative Title: Preparation and structure of WTaFeCrNi high-entropy films for high-throughput screening

YS Li, PK Liaw, Y Zhang
Beijing Advanced Innovation Center of Materials Genome Engineering, State Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing, Beijing 100083, China;
Department of Materials Science and Engineering, The University of Tennessee, Knoxville, Knoxville, TN, United States

 

 
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