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Research and Application of High Entropy Alloys
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Research and Application of High Entropy Alloys

A special issue of Coatings (ISSN 2079-6412). This special issue belongs to the section "Plasma Coatings, Surfaces & Interfaces".

Deadline for manuscript submissions: 29 November 2024 | Viewed by 6055

Special Issue Editor

Dr. Fanli Kong

E-Mail Website
Guest Editor
Innovation Base, Josai International University, Togane 283-8555, Japan
Interests: high-entropy metallic glass; glassy alloys

Special Issue Information

Dear Colleagues,

High-entropy alloys (HEAs) are a new class of metallic materials that contain multiple principal elements in roughly equal atomic proportions, resulting in high configurational entropy and unique microstructures. HEAs have attracted significant attention in recent years due to their potential applications in various fields. This Special Issue invites researchers to contribute their latest findings and progress in the field of HEA research and application. Topics of interest include, but are not limited to the following:

  • Processing and fabrication, and novel alloy design strategies with targeted properties;
  • Mechanical properties and deformation mechanisms;
  • Wear and corrosion resistance;
  • Oxidation resistance and high-temperature stability;
  • Magnetic, electrical, and catalytic properties, and biocompatibility;
  • Computational modeling and simulations;
  • Applications and future directions.

Dr. Fanli Kong
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 alloys
  • mechanical properties
  • corrosion resistance
  • applications
  • microstructure

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Further information on MDPI's Special Issue polices can be found here.

Published Papers (7 papers)

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Research

15 pages, 6565 KiB  
Article
Effect of Over-Aging Degree on Microstructures, Precipitation Kinetics, and Mechanical Properties of an Ultra-High-Strength Al-Zn-Mg-Cu Alloy
by Yuyang Liu, Zhihao Zhao and Gaosong Wang
Coatings 2024, 14(11), 1415; https://doi.org/10.3390/coatings14111415 - 7 Nov 2024
Viewed by 566
Abstract
The effect of over-aging on the precipitation behavior and mechanical properties of an ultra-high-strength Al-Zn-Mg-Cu alloy was investigated using various over-aging treatment regimes. To reveal the influence of over-aging on matrix precipitation, nucleation and coarsening mechanisms were analyzed based on thermodynamic models and [...] Read more.
The effect of over-aging on the precipitation behavior and mechanical properties of an ultra-high-strength Al-Zn-Mg-Cu alloy was investigated using various over-aging treatment regimes. To reveal the influence of over-aging on matrix precipitation, nucleation and coarsening mechanisms were analyzed based on thermodynamic models and calculated precipitation data. Precipitation kinetics at different over-aging degrees were determined through differential scanning calorimetry analysis and the Johnson–Mehl–Avrami–Kolmogorov equations, revealing the activation energy required to precipitate the η’ phase precipitates ranging from 166.08 to 343.28 kJ/mol, and the activation energy required to precipitate the η phase precipitates ranging from 802.03 to 288.42 kJ/mol from the T6 to T73 conditions. In conjunction with a quantitative microstructure analysis, a highly accurate model was developed by systematically calculating the strengthening components of the ultra-high-strength Al-Zn-Mg-Cu alloy under various aging conditions. Full article
(This article belongs to the Special Issue Research and Application of High Entropy Alloys)
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22 pages, 3926 KiB  
Article
Optimization of Laser Cladding Parameters for High-Entropy Alloy-Reinforced 316L Stainless-Steel via Grey Relational Analysis
by Senao Gao, Qiang Fu, Mengzhao Li, Long Huang, Nian Liu, Chang Cui, Bing Yang and Guodong Zhang
Coatings 2024, 14(9), 1103; https://doi.org/10.3390/coatings14091103 - 1 Sep 2024
Cited by 2 | Viewed by 1185
Abstract
Laser cladding technology serves as a pivotal technique in industrial production, especially in the realms of additive manufacturing, surface enhancement, coating preparation, and the repair of part surfaces. This study investigates the influence of metal powder composition and processing parameters on laser cladding [...] Read more.
Laser cladding technology serves as a pivotal technique in industrial production, especially in the realms of additive manufacturing, surface enhancement, coating preparation, and the repair of part surfaces. This study investigates the influence of metal powder composition and processing parameters on laser cladding coatings utilizing the Taguchi orthogonal experimental design method. To optimize the laser cladding parameters, multi-response grey relational analysis (GRA) was employed, aiming to improve both the microhardness and the overall quality of the coatings. The optimal parameter combinations identified through GRA were subsequently validated through experimental tests. The results reveal that the microhardness and quality of the coatings are substantially influenced by several critical factors, including the powder feed rate, laser power, high-entropy alloy (HEA) addition rate, scanning speed, and substrate tilt angle. Specifically, the powder feed rate exerts the most significant effect on the microhardness, dilution rate, and average contact angle. In contrast, laser power primarily impacts the mean contact angle difference. The HEA addition rate notably affects the mean contact angle difference, while the scanning speed affects the microhardness and the substrate tilt angle influences the average contact angle. The results of the validation experiment showed a deviation of only 0.95% from the predicted values, underscoring the efficacy of the grey relational analysis (GRA) in optimizing the laser cladding process parameters. The methodology presented in this paper can be applied to determine the ideal processing parameters for multi-response laser cladding processes, encompassing applications such as surface peening and surface repair. Full article
(This article belongs to the Special Issue Research and Application of High Entropy Alloys)
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12 pages, 7017 KiB  
Article
Microstructures and Properties of Laser-Cladded FeCoCrNiAlTi High-Entropy Alloy with Intensive Repair Potential
by Hao Yu, Bo Liu, Debin Wang, Guofeng Han, Dong Han and Baijun Yang
Coatings 2024, 14(8), 1068; https://doi.org/10.3390/coatings14081068 - 21 Aug 2024
Viewed by 785
Abstract
As a key step in intensive additive repair, the design of intensive repair materials immediately needs to be explored. In this work, an intensive additive repair study based on laser cladding technology was performed using a self-designed Fe20Co25Ni31 [...] Read more.
As a key step in intensive additive repair, the design of intensive repair materials immediately needs to be explored. In this work, an intensive additive repair study based on laser cladding technology was performed using a self-designed Fe20Co25Ni31Cr8Al9Ti7 high-entropy alloy (HEA) powder and three types of substrates widely used in field equipment (namely, Q235, 17CrNiMo6H, and 304 stainless steel). The results revealed that the HEA repair layer (HEA-RL) consists of a dominant FCC phase and a small amount of BCC phase, and the microstructure shows the columnar-to-equiaxed grain transition behavior. The metallurgical bonding between the HEA-RL and the three substrates has almost no defects. Compared with the three substrates, the HEA-RL has a much higher microhardness (~340 HV) and decent corrosion resistance. Therefore, the underlying mechanisms for the microstructure and performance of the HEA-RL were also discussed. This work provides a new idea for the design of intensive repair materials. Full article
(This article belongs to the Special Issue Research and Application of High Entropy Alloys)
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13 pages, 6862 KiB  
Article
Effect of Heat Treatment Temperature on the Microstructure and Mechanical Properties of Cu0.3Cr2Fe2Ni3Mn2Nbx High-Entropy Alloys
by Fuqiang Guo, Chunyan Wang and Bo Ren
Coatings 2024, 14(8), 950; https://doi.org/10.3390/coatings14080950 - 30 Jul 2024
Viewed by 709
Abstract
The effects of heat treatment temperature on the microstructure and mechanical properties of Cu0.3Cr2Fe2Ni3Mn2Nbx high-entropy alloys (HEAs) were studied. Results indicate that in the as-cast state, an Nb0 alloy is composed [...] Read more.
The effects of heat treatment temperature on the microstructure and mechanical properties of Cu0.3Cr2Fe2Ni3Mn2Nbx high-entropy alloys (HEAs) were studied. Results indicate that in the as-cast state, an Nb0 alloy is composed of a single FCC phase, and a Laves phase gradually forms as Nb content increases. After heat treatment at 800 °C, BCC solid solution phases rich in Cr, Fe, and Mn form in all alloys. The BCC phases in the Nb0.2 and Nb0.4 alloys decompose after heat treatment at 900 and 1000 °C, respectively, and the microhardness of the as-cast Cu0.3Cr2Fe2Ni3Mn2Nbx HEAs increases from 127 to 203 HV with increasing Nb content. After heat treatment, the microhardness of the alloys considerably improves, and the Nb0.4 alloy has the highest microhardness after heat treatment at 800 °C (approximately 346 HV). After heat treatment at 900 and 1000 °C, the microhardness of the three alloys decreases. The yield strength of the as-cast Cu0.3Cr2Fe2Ni3Mn2Nbx HEAs increases with Nb content and shows a trend of first increasing and then decreasing with increasing heat treatment temperature. The strengthening mechanism of the heat-treated alloys is mainly attributed to the second-phase strengthening of the Laves phase and the solid solution strengthening of the BCC phase. Full article
(This article belongs to the Special Issue Research and Application of High Entropy Alloys)
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11 pages, 4100 KiB  
Article
The Effects on Stability and Electronic Structure of Si-Segregated θ′/Al Interface Systems in Al-Cu Alloys
by Lu Jiang, Zhihao Zhao and Gaosong Wang
Coatings 2024, 14(7), 879; https://doi.org/10.3390/coatings14070879 - 13 Jul 2024
Viewed by 905
Abstract
This study systematically investigates the energy and electronic properties of Si-segregated θ′(Al2Cu)/Al semi-coherent and coherent interface systems in Al-Cu alloys using ab initio calculations. By evaluating the bonding strength at the interface, it has been revealed that Si segregated at the [...] Read more.
This study systematically investigates the energy and electronic properties of Si-segregated θ′(Al2Cu)/Al semi-coherent and coherent interface systems in Al-Cu alloys using ab initio calculations. By evaluating the bonding strength at the interface, it has been revealed that Si segregated at the A1 site (Al slab) of the semi-coherent interface systems exhibits the most negative segregation energy, resulting in a noticeable decrease in total energy and an increase in interface adhesion. The electronic structure analysis indicates the presence of Al-Cu and Al-Al bonds, with Si occupying the A1 site. The strong bond formation between Al-Cu and Al-Al is essential for improving interface bonding strength. The results of the calculating analyses are consistent with the results of the previous experiments, and Si can be used as a synergistic element to reduce the θ′/Al interface energy and further reduce the coarsening drive of the θ′ precipitated phase, which can provide new perspectives and computational ideas for the compositional design of heat-resistant Al-Cu alloys. Full article
(This article belongs to the Special Issue Research and Application of High Entropy Alloys)
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11 pages, 7890 KiB  
Article
Effect of Cooling Method on Microstructure and Microhardness of CuCrFeMnNi High-Entropy Alloy
by Yajun Zhou, Ruifeng Zhao, Hechuan Geng, Bo Ren, Zhongxia Liu, Jianxiu Liu, Aiyun Jiang and Baofeng Zhang
Coatings 2024, 14(7), 831; https://doi.org/10.3390/coatings14070831 - 3 Jul 2024
Viewed by 693
Abstract
This study investigated four cooling methods for CuCrFeMnNi high-entropy alloy, namely, furnace cooling, air cooling, oil cooling, and water cooling (designated as FC, AC, OC, and WC, respectively), following a 12 h treatment at 800 °C. Results indicate that all four cooled alloys [...] Read more.
This study investigated four cooling methods for CuCrFeMnNi high-entropy alloy, namely, furnace cooling, air cooling, oil cooling, and water cooling (designated as FC, AC, OC, and WC, respectively), following a 12 h treatment at 800 °C. Results indicate that all four cooled alloys consisted of two FCC solid-solution phases (FCC1 and FCC2) and ρ phases. However, the FC alloy primarily contained FCC2 as the main phase and FCC1 as the secondary phase. The other three cooling methods yielded alloys with FCC2 as the primary phase and FCC1 as the secondary phase. With an increase in cooling rate, the content of the FCC1 phase gradually increased, that of the ρ phase initially decreased and then increased, and that of the FCC2 phase gradually decreased. The microstructure of the CuCrFeMnNi high-entropy alloy under the four cooling methods consisted of gray-black dendrites rich in Cr-Fe and white dendrites rich in Cu. Black ρ-phase particles predominated the dendrite region. As the cooling rate increased, the white interdendritic regions shrank, and the gray-black interdendritic regions expanded. The FC alloy exhibited the lowest microhardness at approximately 202.6 HV. As the cooling rate increased, the microhardness of the alloy progressively increased. The microhardness of the WC alloy was the highest, at approximately 355 HV. The strengthening mechanisms for all the alloys were primarily solid-solution strengthening and second-phase precipitation strengthening. Full article
(This article belongs to the Special Issue Research and Application of High Entropy Alloys)
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9 pages, 3098 KiB  
Communication
Predicting New Single/Multiphase-Structure High-Entropy Alloys Using a Pattern Recognition Network
by Fang Wang, Jiahao Wang, Jiayu Wang, Ruirui Wu and Ke Liu
Coatings 2024, 14(6), 690; https://doi.org/10.3390/coatings14060690 - 1 Jun 2024
Viewed by 826
Abstract
Machine learning methods were employed to predict the phase structures of high-entropy alloys (HEAs). These alloys were classified into four categories: bcc (body-centered cubic), fcc (face-centered cubic), bcc+fcc (body-centered cubic and face-centered cubic) and others (containing intermetallic compounds and other structural alloys). The [...] Read more.
Machine learning methods were employed to predict the phase structures of high-entropy alloys (HEAs). These alloys were classified into four categories: bcc (body-centered cubic), fcc (face-centered cubic), bcc+fcc (body-centered cubic and face-centered cubic) and others (containing intermetallic compounds and other structural alloys). The utilized algorithm was a Pattern Recognition Network (PRN) utilizing cross-entropy as the loss function, enabling the prediction of HEAs’ phase formation probability. The PRN algorithm demonstrated an accuracy exceeding 87% based on the test data. The PRN algorithm successfully predicted the transformation from fcc to fcc+bcc and subsequently to a bcc structure with the increase in Al content in AlxCoCu6Ni6Fe6 and AlxCoCrCuNiFe HEAs. In addition, AlxCoCu6Ni6Fe6 (x = 1, 3, 6, 9) HEAs were prepared using a vacuum arc furnace, and the microstructure of the as-cast alloy was tested by means of XRD, SEM, and EBSD, confirming the high consistency between the predicted and observed phase structures. This study showcases the efficacy of the PRN algorithm in predicting both single- and multiphase-structure high-entropy alloys, offering valuable insights into alloy design and development. Full article
(This article belongs to the Special Issue Research and Application of High Entropy Alloys)
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