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Innovations and Thermal Stability of High-Entropy Alloys
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Innovations and Thermal Stability of High-Entropy Alloys

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

Deadline for manuscript submissions: closed (20 August 2023) | Viewed by 5498

Special Issue Editor

Prof. Dr. Yuexia Wang

E-Mail Website
Guest Editor
Key Laboratory of Nuclear Physics and Ion-beam Application (MOE), Institute of Modern Physics, Department of Nuclear Science and Technology, Fudan University, Shanghai 200433, China
Interests: computer simulation; physical properties in materials; irradiation damage

Special Issue Information

Dear Colleagues,

According to the alloy design with multiple principal elements in the equimolar of near-equimolar ratios—high-entropy alloys (HEAs)—435,897 alloys can be synthesized, provided that 5 of the current 37 kinds of elements commonly used in the preparation of HEAs are mixed together. If the number of principals is set to 3 to 6, this number will reach 2,834,496. At present, 400 kinds of HEAs have been developed, many of which are obtained by means of adjustment according to the existing formula. However, less than 100 HEAs have actually been obtained through mixing different elements so far. This means that there is still tremendous room for exploiting HEAs. To date, many compositions have been designed and the corresponding properties have been investigated, such as mechanical properties, conductivity, electrocatalysis, and even those related to biomaterials. However, the compositions and lattice distortions of HEAs are different from each other even with the same structure, which remarkably raises the difficulty of predicting the behaviors of materials, particularly from the perspective of the micro-structure. Profound physics, which is rooted in the correlation between the intrinsic structural characteristics and properties, is still lacking a large number of journal papers that address HEAs. In addition, as the temperature decreases, the impact of the entropy on Gibbs free energy is attenuated, the chemical disorder in the matrix may be changed, or even element segregation or phase precipitation can easily occur, which may influence the stability of properties. Thus, the stability of properties with temperature should be another important issue for HEAs, different from traditional alloys whose properties are generally stable in a somehow large temperature range. In any case, the difference between local chemical environment and the lattice distortion in HEAs provide us with novel phenomena in chemistry and physics, distinct from traditional alloys. The exciting exploitation and application of these potentially novel properties are expected in future.

Prof. Dr. Yuexia Wang
Guest Editor

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Keywords

  • grain boundary segregation
  • solid solution
  • correlation between properties and micro-structure
  • mechanical properties
  • conductivity
  • machine learning in HEAs
  • application (hydrogen storage)
  • biomaterials
  • oxygen electrocatalysis
  • superconductivity

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Published Papers (3 papers)

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Research

12 pages, 3680 KiB  
Article
Significantly Improving the High-Temperature Tensile Properties of Al17Cr10Fe36Ni36Mo1 Alloys by Microalloying Hf
by Zhihua Chen, Jianbin Wang, Yuhao Jia, Qingfeng Wu, Xiaoming Liu, Linxiang Liu, Junjie Li, Feng He, Zhijun Wang and Jincheng Wang
Materials 2023, 16(21), 6836; https://doi.org/10.3390/ma16216836 - 24 Oct 2023
Cited by 5 | Viewed by 1386
Abstract
Dual-phase high-entropy alloys with excellent room temperature and high-temperature properties have been widely studied as potential high-temperature structural materials. However, interface weakening causes its high-temperature performance to decline at higher temperatures, severely limiting further development. In this study, a series of Al17 [...] Read more.
Dual-phase high-entropy alloys with excellent room temperature and high-temperature properties have been widely studied as potential high-temperature structural materials. However, interface weakening causes its high-temperature performance to decline at higher temperatures, severely limiting further development. In this study, a series of Al17Cr10Fe36Ni36Mo1Hfx (x = 0, 0.03, 0.15, 0.3, 0.5, and 0.8 at%) alloys were prepared to study the effect of Hf content on the microstructure and mechanical properties of the matrix alloy. The results indicate that with the addition of the Hf, the Hf-rich phase began to precipitate at the interface and inside the B2 phase in the matrix alloy. In contrast, the morphology of both the FCC and B2 phases had no noticeable change. With the increase in Hf content, the high-temperature strength and ductility of the alloy first increased and then decreased, while the room temperature performance remained almost unchanged. Benefiting from the hindrance of the Hf-rich phase to grain boundary sliding and dislocation movement during high-temperature deformation, the tensile strength, yield strength, and plasticity of the matrix alloy increased from 474 MPa, 535 MPa, and 8.7% to 816 MPa, 923 MPa, and 42.0% for the Al17Cr10Fe36Ni36Mo1Hf0.5 alloys, respectively. This work provides a new path for designing a high-entropy alloy with excellent high-temperature mechanical properties. Full article
(This article belongs to the Special Issue Innovations and Thermal Stability of High-Entropy Alloys)
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13 pages, 59490 KiB  
Article
Thermal Stability and Hot Corrosion Performance of the AlCoCrFeNi2.1 High-Entropy Alloy Coating by Laser Cladding
by Li Zhang, Yan Ji and Bin Yang
Materials 2023, 16(17), 5747; https://doi.org/10.3390/ma16175747 - 22 Aug 2023
Cited by 4 | Viewed by 1663
Abstract
Both crack-free AlCoCrFeNi2.1 eutectic high-entropy alloy (EHEA) and Y and Hf co-doping AlCoCrFeNi2.1 EHEA (YHf-EHEA) coatings were prepared by laser cladding. The solidification microstructure, thermal stability, and hot corrosion performance of the coatings at 900 °C under 75% Na2SO [...] Read more.
Both crack-free AlCoCrFeNi2.1 eutectic high-entropy alloy (EHEA) and Y and Hf co-doping AlCoCrFeNi2.1 EHEA (YHf-EHEA) coatings were prepared by laser cladding. The solidification microstructure, thermal stability, and hot corrosion performance of the coatings at 900 °C under 75% Na2SO4 + 25% NaCl molten salts were investigated. The experimental results showed that the structure of the as-deposited coatings consisted of FCC and BCC/B2 phases. After heat treatment, an Al-rich L12 phase was precipitated in the FCC phase of all coatings. The grain sizes of the EHEA and YHf-EHEA coatings after heat treatment at 900 °C for 10 h increased by 27.5% and 15.7%, respectively, compared to the as-deposited coatings. Meanwhile, after hot corrosion, the spallation areas of the YHf-EHEA and EHEA coatings accounted for 14.98% and 5.67% of the total surface area, respectively. In this study, the Y and Hf co-doping did not change the microstructure morphology and phase structure of the coatings but did improve the thermal stability and resistance of the hot corrosion oxide scale spallation, providing a certain amount of data and theoretical support for the application of EHEA coatings as high-temperature protective coatings. Full article
(This article belongs to the Special Issue Innovations and Thermal Stability of High-Entropy Alloys)
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16 pages, 10826 KiB  
Article
Composition and Structure of NiCoFeCr and NiCoFeCrMn High-Entropy Alloys Irradiated by Helium Ions
by Bauyrzhan Amanzhulov, Igor Ivanov, Vladimir Uglov, Sergey Zlotski, Azamat Ryskulov, Alisher Kurakhmedov, Mikhail Koloberdin and Maxim Zdorovets
Materials 2023, 16(10), 3695; https://doi.org/10.3390/ma16103695 - 12 May 2023
Cited by 9 | Viewed by 1944 | Correction
Abstract
High-entropy alloys (HEAs) have prospects for use as nuclear structural materials. Helium irradiation can form bubbles deteriorating the structure of structural materials. The structure and composition of NiCoFeCr and NiCoFeCrMn HEAs formed by arc melting and irradiated with low-energy 40 keV He2+ [...] Read more.
High-entropy alloys (HEAs) have prospects for use as nuclear structural materials. Helium irradiation can form bubbles deteriorating the structure of structural materials. The structure and composition of NiCoFeCr and NiCoFeCrMn HEAs formed by arc melting and irradiated with low-energy 40 keV He2+ ions and a fluence of 2 × 1017 cm−2 have been studied. Helium irradiation of two HEAs does not change the elemental and phase composition, and does not erode the surface. Irradiation of NiCoFeCr and NiCoFeCrMn with a fluence of 5 × 1016 cm−2 forms compressive stresses (−90 … −160 MPa) and the stresses grow over −650 MPa as fluence increases to 2 × 1017 cm−2. Compressive microstresses grow up to 2.7 GPa at a fluence of 5 × 1016 cm−2, and up to 6.8 GPa at 2 × 1017 cm−2. The dislocation density rises by a factor of 5–12 for a fluence of 5 × 1016 cm−2, and by 30–60 for a fluence of 2 × 1017 cm−2. Stresses and dislocation density in the HEAs change the most in the region of the maximal damage dose. NiCoFeCrMn has higher macro- and microstresses, dislocation density, and a larger increase in their values, with an increasing helium ion fluence compared to NiCoFeCr. NiCoFeCrMn a showed higher radiation resistance compared to NiCoFeCr. Full article
(This article belongs to the Special Issue Innovations and Thermal Stability of High-Entropy Alloys)
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