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Crystals
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Advances of High Entropy Alloys
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Advances of High Entropy Alloys

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

Deadline for manuscript submissions: 30 November 2024 | Viewed by 5551

Special Issue Editors

Dr. Long Meng

E-Mail Website
Guest Editor
Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190, China
Interests: pyrometallurgy; hydrometallurgy; extractive metallurgy; recovery and separation; secondary resources; mineral extraction
Special Issues, Collections and Topics in MDPI journals
Dr. Xiaoming Sun

E-Mail Website
Guest Editor
Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190, China
Interests: wave-transparent materials; transparent ceramics; high entropy alloys; shape memory alloys; X-ray diffraction; phase transformations; material processing; mechanical behavior of materials; neutron diffraction; synchrotron radiation

Special Issue Information

Dear Colleagues,

In the past decade, the sudden rise of high entropy alloys (HEAs) has become a research hotspot in the domain of metal materials. HEAs are generally considered to be composed of five or more principal elements and the atomic percentage of each principal element is between 5 at.% and 35 at.%. This unique design concept means that these alloys exhibit high entropy effects in regard to thermodynamics and other characteristics, such as the lattice distortion effect, the sluggish diffusion effect and cocktail effect. Owing to their remarkable and peculiar characteristics, HEAs exhibit excellent properties, such as balanced strength and ductility, wear resistance, anti-oxidation and outstanding corrosion resistance.

We invite researchers to contribute to this Special Issue on “High Entropy Alloys”, which is intended to serve as a unique multidisciplinary forum, covering broad aspects of the science, technology, and application of high entropy alloys.

Potential topics include, but are not limited to, the following:

  • Synthesis of high entropy alloys;
  • Characteristics of structural properties;
  • Excellent properties;
  • Applications.

Dr. Long Meng
Dr. Xiaoming Sun
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
  • corrosion-resistant properties
  • mechanical properties
  • microstructures
  • anti-oxidation properties
  • passivation properties
  • electrochemical properties

Published Papers (4 papers)

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Research

18 pages, 12031 KiB  
Article
Microstructure and Texture Evolution of a Dynamic Compressed Medium-Entropy CoCr0.4NiSi0.3 Alloy
by Li Zhang, Weiqiang Zhang, Lijia Chen, Feng Li, Hui Zhao, Xin Wang and Ge Zhou
Crystals 2023, 13(9), 1390; https://doi.org/10.3390/cryst13091390 - 18 Sep 2023
Cited by 2 | Viewed by 874
Abstract
Focal research has been conducted on medium-entropy alloys (MEAs) that exhibit a balanced combination of strength and plasticity. In this study, the microstructure, dynamic mechanical properties, and texture evolution of an as-cast medium-entropy CoCr0.4NiSi0.3 alloy were investigated through dynamic compression [...] Read more.
Focal research has been conducted on medium-entropy alloys (MEAs) that exhibit a balanced combination of strength and plasticity. In this study, the microstructure, dynamic mechanical properties, and texture evolution of an as-cast medium-entropy CoCr0.4NiSi0.3 alloy were investigated through dynamic compression tests at strain rates ranging from 2100 to 5100 s−1 using the Split Hopkinson Pressure Bar in order to elucidate the underlying dynamic deformation mechanism. The results revealed a significant strain rate effect with dynamic compressive yield strengths of 811 MPa at 2100 s−1, 849 MPa at 3000 s−1, 919 MPa at 3900 s−1, and 942 MPa at 5100 s−1. Grains were dynamically refined from 19.73 to 3.35 μm with increasing strain rates. The correlation between adiabatic temperature rise induced by dynamic compression and dynamic recrystallization was examined, revealing that the latter is not associated with adiabatic heating but rather with phase transition triggered by the dynamic stress during compression. The proportion of Σ3n (1 ≤ n ≤ 3) grain boundaries in deformation specimens increases with increasing strain rates during dynamic compression. The formation of specific three-node structures enhances both strength and plasticity by impeding crack propagation and resisting higher mechanical stress. In the as-cast state, significant anisotropy was observed in the MEA. As strain rates increased, it transited into a stable {111}<112> F texture. The exceptional dynamic properties of strength and plasticity observed in the as-cast state of the MEA can be attributed to a deformation mechanism involving a transition from dislocation slip to the formation of intricate arrangements, accompanied by interactions encompassing deformation nanotwins, stacking faults, Lomer–Cottrell locks, stair-rods, and displacive phase transformations at elevated strain rates. Full article
(This article belongs to the Special Issue Advances of High Entropy Alloys)
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13 pages, 22202 KiB  
Article
High-Temperature Oxidation Behaviors of AlCrTiSi0.2 High-Entropy Alloy Doped with Rare Earth La and Y
by Lingsheng Ke, Long Meng, Sheng Fang, Chun Lin, Mingtian Tan and Tao Qi
Crystals 2023, 13(8), 1169; https://doi.org/10.3390/cryst13081169 - 27 Jul 2023
Cited by 1 | Viewed by 675
Abstract
High-entropy alloys (HEAs) were prepared with strong antioxidant metals Al, Cr, Ti, and Si as matrix elements, and the effects of rare earth (RE) lanthanum (La) and yttrium (Y) doping on their microstructures and high-temperature oxidation resistance were explored in this study. The [...] Read more.
High-entropy alloys (HEAs) were prepared with strong antioxidant metals Al, Cr, Ti, and Si as matrix elements, and the effects of rare earth (RE) lanthanum (La) and yttrium (Y) doping on their microstructures and high-temperature oxidation resistance were explored in this study. The AlCrTiSi0.2RE0.02 HEAs were prepared by using vacuum arc melting and were oxidized mass gain at 1000 °C. After oxidation for 53 h, AlCrTiSi0.2 HEA had a mass increase of 1.195 mg/cm2, and it had the best oxidation resistance of three HEAs (AlCrTiSi0.2, AlCrTiSi0.2La0.02, and AlCrTiSi0.2Y0.02). The surface oxide layers of three HEAs mainly consisted of Al and Ti oxides; the layered oxide film of AlCrTiSi0.2 alloy was mainly composed of dense Al2O3, and the acicular oxide films of AlCrTiSi0.2La0.02 and AlCrTiSi0.2Y0.02 alloys were primarily composed of loose Ti oxide. Doping La and Y decreased the oxidation resistance of AlCrTiSi0.2. In the early stage of oxidation of rare earth HEAs, the surface oxide layer was loose because La and Y reacted with the matrix metal, which slowed down the diffusion of element Al or accelerated the diffusion of element Ti. In the late stage of oxidation, La and Y interacted with O and entered the matrix metal to form rare earth oxides. Full article
(This article belongs to the Special Issue Advances of High Entropy Alloys)
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13 pages, 11367 KiB  
Article
Organizational Evolution during Performance Meritocracy of AlSi0.5CrxCo0.2Ni Lightweight High Entropy Alloys
by Mingtian Tan, Long Meng, Sheng Fang, Chun Lin, Lingsheng Ke, Zhihui Yu, Jingkui Qu and Tao Qi
Crystals 2022, 12(12), 1828; https://doi.org/10.3390/cryst12121828 - 15 Dec 2022
Cited by 2 | Viewed by 1956
Abstract
The Al-Si-Cr-Co-Ni High Entropy Alloy (HEA) with low density (about 5.4 g/cm3) and excellent performance had significant potential in the lightweight engineering material field. To further research and optimize the Al-Si-Cr-Co-Ni system HEA, the influences of element Cr on the microstructures [...] Read more.
The Al-Si-Cr-Co-Ni High Entropy Alloy (HEA) with low density (about 5.4 g/cm3) and excellent performance had significant potential in the lightweight engineering material field. To further research and optimize the Al-Si-Cr-Co-Ni system HEA, the influences of element Cr on the microstructures and performances of lightweight AlSi0.5CrxCo0.2Ni (in mole ratio, x = 1.0, 1.2, 1.4, 1.6, and 1.8) HEAs were investigated. The experiment results manifested that AlSi0.5CrxCo0.2Ni HEAs were composed of A2 (Cr-rich), B2 (Ni-Al), and Cr3Si phases, indicating that the addition of Cr did not result in the formation of a new phase. However, ample Cr increased the Cr3Si phase composition, further ensuring the high hardness (average HV 981.2) of HEAs. Electrochemical tests demonstrated that HEAs with elevated Cr3Si and A2 phases afforded greater corrosion resistance, and the improvement in corrosion was more pronounced when x > 1.6. This work is crucial in the development of lightweight engineering HEAs, which are of tremendous practical utility in the fields of cutting tools, hard coating, etc. Full article
(This article belongs to the Special Issue Advances of High Entropy Alloys)
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13 pages, 5826 KiB  
Article
Carbon Nanotubes (CNTs) Reinforced CoCrMoNbTi0.4 Refractory High Entropy Alloy Fabricated via Laser Additive Manufacturing: Processing Optimization, Microstructure Transformation and Mechanical Properties
by Xuyang Ye, Mina Zhang, Dafeng Wang, Longjun He, Zifa Xu, Yuhang Zhou, Dianbo Ruan and Wenwu Zhang
Crystals 2022, 12(11), 1678; https://doi.org/10.3390/cryst12111678 - 21 Nov 2022
Cited by 4 | Viewed by 1414
Abstract
Refractory high-entropy alloys (RHEAs) exhibit outstanding softening resistance and thermal stability at elevated temperatures. Unfortunately, poor ductility at room temperature has remained the critical issue for their processability and practical application. In this study, an original-type fabrication method of RHEA was proposed, using [...] Read more.
Refractory high-entropy alloys (RHEAs) exhibit outstanding softening resistance and thermal stability at elevated temperatures. Unfortunately, poor ductility at room temperature has remained the critical issue for their processability and practical application. In this study, an original-type fabrication method of RHEA was proposed, using multi-walled carbon nanotubes (MWCNTs) to enhance the alloy prepared via laser melting deposition (LMD) technology. The processing optimization, microstructure evolution and mechanical properties were systematically investigated for LMD processing of CNTs/CoCrMoNbTi0.4 RHEA. The results have shown that CNTs/CoCrMoNbTi0.4 RHEA have a polycrystalline structure (BCC, HCP, and TiC). As the optimal LMD-processing parameters of laser linear energy density of 3.6 J/mm were applied, owing to the formation of high densification and an ultrafine microstructure, the fully dense LMD-processed alloy exhibited high microhardness of 1015 HV0.5, fracture strength of 2110.5 MPa, and fracture strain of 2.39%. The solid solution strengthening and load transfer are considered as the main strengthening mechanisms occurring simultaneously during compressive tests at room temperature, leading to excellent mechanical properties of LMD-processed CNTs/CoCrMoNbTi0.4 RHEA, which explores the potential application of RHEAs. Full article
(This article belongs to the Special Issue Advances of High Entropy Alloys)
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