High Entropy Alloys（2021）

Research Progress on Deformation Mechanisms Under Dynamic Loading of High-Entropy Alloys Article

WANG Ruixin, TANG Yu, LI Shun, BAI Shuxin

Materials Reports 2021,35(17 ):17001 -17009. DOI:10.11896/cldb.21040273

Abstract （1578）

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Study on Strengthening Methods of AlCoCrFeNi High-Entropy Alloys Article

LI Hongchao, WANG Jun, YUAN Ruihao, WANG Yi, KOU Hongchao, LI Jinshan

Materials Reports 2021,35(17 ):17010 -17018. DOI:10.11896/cldb.21020106

Abstract （1452）

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Save High-entropy alloys (HEAs) is also called multi-principal element alloys. Compared with traditional alloys with one or two elements as the principal constituents, the multiple constituent elements design concept of HEAs grants them the unique constituent, phase structure and a series of excellent mechanical properties. Especially in recent years, there are a lot of HEAs with high strength and ductility, which is of great significance to their engineering application. The excellent mechanical performance is closely related to the strengthening mechanism of the alloys, such as grain-boundary strengthening, coherent second phase strengthening and heterogeneous structure strengthening mechanism, which all promote the improvement of the performance of HEAs in various degrees. Therefore, it is crucial to understand the strengthening mechanism of the HEAs in order to improve the mechanical properties of the HEAs and explore new high-strength and high-ductility HEAs. AlCoCrFeNi HEAs is currently one of the most studied HEAs, which can produce different structure through composition adjustment and different thermo-mechanical treatment process, thus inducing different strengthening mechanism. The mechanical properties of AlCoCrFeNi HEAs can be adjusted in a wide range, making it an ideal material to study the strengthening mechanism of HEAs. Based on this, this article focuses on the subject of the strengthening mechanism of AlCoCrFeNi HEAs.
In this article, the strengthening mechanism of HEAs in recent years are reviewed, including grain-boundary strengthening, coherent second phase strengthening, incoherent second phase strengthening and heterogeneous structure strengthening. The composition and structure control for HEAs strengthening mechanism and mechanical properties is further expounded. In addition, this paper proposes that the single strengthening mechanism cannot greatly improve the strength of the alloy. By summarizing the multiple strengthening mechanism, it is proposed that the higher strength can be achieved by combining multiple strengthening mechanisms. At last, the future perspective of strengthening mechanism in HEAs is also discussed.

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Research Progress on the Design, Preparation and Properties of High-entropy Metallic Glasses Article

CHONG Kai, ZHANG Zhibin, ZOU Yong, LIANG Xiubing

Materials Reports 2021,35(17 ):17019 -17025. DOI:10.11896/cldb.20120197

Abstract （1217）

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Save High-entropy metallic glasses High-entropy metallic glasses are an emerging class of materials that show promising potential forvarious engineering applications because of their advantageous characteristics of high-entropy alloy composition and amorphous alloy structure. Owing to their excellent mechanical and physical properties, these metallic glasses have recently attracted increased attention. Research on related high-entropy metallic glasses is still in its infancy. In this study, the bases for designing the composition of high-entropy metallic glasses are introduced, and the effects of key physical parameters, such as mixing entropy (ΔS_mix), mixing enthalpy (ΔH_mix), and atomic mismatch (δ), on the microstructures of high-entropy metallic glasses are comprehensively analyzed. Moreover, the current status of the study of alloys systems, preparation methods, and mechanical and physical properties is discussed and summarized. Material systems of high-entropy metallic glasses that have been developed remain limited. Current methods for preparing high-entropy metallic glasses have inherited the characteristics of those for preparing amorphous alloys and high-entropy alloys. These methods can be roughly divided into liquid-phase preparation, gas-phase preparation, and solid-phase preparation. Owing to their excellent thermodynamic properties, high-entropy amorphous materials are expected to break through the size limit through thermal spraying and achieve large-scale applications. Research on the properties of high-entropy metallic glasses mainly focuses on mechanical properties, corrosion resistance, magnetic properties, amorphous-forming ability, and thermal stability. Among these topics of interest, the influence of high-entropy on the amorphous formation, structure, thermodynamic properties, and abnormal thermal stability of high-entropy metallic glasses must be urgently resolved. Potential topics on studies of material systems of high-entropy metallic glasses on the basis of the concept of material genetic engineering are explored. The application prospects of such materials are also discussed.

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Effect of C on Microstructure and Mechanical Properties of CoFe₂NiV_0.5Mo_0.2 High Entropy Alloy Article

ZHANG Guojia, LI Ren, LIU Dehua, LU Yiping, WANG Tongmin, LI Tingju

Materials Reports 2021,35(17 ):17026 -17030. DOI:10.11896/cldb.21010131

Abstract （827）

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Research Status on the Application of High-entropy Alloys in Dissimilar Metal Welding Article

WU Zhenggang, LI Xi, LI Zhongtao

Materials Reports 2021,35(17 ):17031 -17036. DOI:10.11896/cldb.21060252

Abstract （1393）

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Advances of the Strengthening and Toughening of High-entropy Multi-principal-element Heat-resistant Alloys Article

GAO Niu, LIU Xinwang, WU Weifeng, BAI Zhucheng, YAO Junqing, FAN Zitian

Materials Reports 2021,35(17 ):17037 -17042. DOI:10.11896/cldb.21040085

Abstract （972）

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Research Progress of Strategies for Improving Strength-ductility Combinations and Mechanical Properties of High Entropy Alloys Article

WANG Weitong, CHEN Shuying, ZHANG Yong, ZHAO Yonghao

Materials Reports 2021,35(17 ):17043 -17050. DOI:10.11896/cldb.20080303

Abstract （1270）

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Save Since the high entropy alloy has been reported for the first time, its excellent mechanical properties have attracted wide attention from all over the world. The superior strength, high hardness, good resistance to wear and corrosion of the high entropy alloy and its excellent service ability at extreme temperatures illustrate that the high entropy alloy has great potential in industrial applications in the future. With the increasing investigation of high entropy alloys, from the variation of elemental types, and the proportion of principal elements, the optimization and development of mechanical properties of high entropy alloys are accompanied by structural changes. Nevertheless, the mechanical properties of high entropy alloys still have much room for improvement. Therefore, how to rationally design the composition and microstructure and enhance the mechanical properties of high entropy alloys is a hot topic at present.
In high entropy alloys, the existing strengthening and toughening methods include fine-grained strengthening, solid solution strengthening and toughening, eutectic structure strengthening and toughening, TWIP (twinning induced plasticity) effect strengthening and toughening, TRIP (transformation induced plasticity) effect strengthening and toughening, and precipitate strengthening and toughening. Fine-grained strengthening and precipitate strengthening exist in most high entropy alloys and it is easy to achieve by thermomechanical treatment. Therefore, how to establish the correlation between the strengthening mechanisms, microstructural characteristics and mechanical properties is a critical issue at present.
In present paper, the research progress of strengthening and toughening methods in high entropy alloys is summarized, and the design concepts of solid solution strengthening, SRO (short-range ordering) strengthening, precipitate strengthening and heterogeneous strengthening and toughening were introduced as well. We also discuss the effect of various special structures on the deformation mechanism and mechanical pro-perties of high entropy alloy. The problems and development prospects of the high entropy alloy in the research process are also analyzed, in order to provide important reference for the subsequent establishment of effective connection between the microstructural characteristics and the mechanical properties.

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The Progress of High-entropy Alloys with the Functional Properties Article

DU Yuhang, DING Deyu, GUO Ning, GUO Shengfeng

Materials Reports 2021,35(17 ):17051 -17063. DOI:10.11896/cldb.21030186

Abstract （1852）

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Save For the traditional alloys, most of which were based on a single principal element. They improved the comprehensive properties of the mate-rials always by adding a small or tiny number of specific elements. However, it limited the development of their components and novel pro-perties to a large extent. Therefore, it is high time to develop unconventional alloys to meet the increasing demands. High-entropy alloys (HEAs), a new type of multi-element metals found in recent years, have been gaining increasing popularity among lots of researchers within just these few years because of its unique design concept, organizational structure and excellent properties. Compared with the traditional ones which focused on the boundary (vertex, edge) region of the phase diagram, HEAs attach more importance to the region near the center of the multi-component phase diagram, which is why HEAs have a wider space for the development of composition design. Besides, high-entropy alloys exhibit excellent mechanical properties and good functional properties. Currently, most researches on HEAs focus on the microstructure and mechanical properties of structural materials. According to the composition design and deformation mechanism of HEAs have made great progress. However, the theoretical researches on the functional properties of high-entropy alloys are still very limited. Therefore, this study not only briefly introduces the development of HEAs and systematically summarizes the preparation methods of HEAs, but also discusses the research status of corrosion resis-tance and wear resistance in detail and then summarizes the main factors affecting these properties. In addition, attention has also been paid to the current research status of HEAs as soft magnetic, anti-radiative, catalytic, biomedical materials. Finally, the critical issues of the present research and future development of high-entropy alloys are prospected. The current review would provide the useful reference for scientists who conduct researches on the functional HEAs.

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Research Progress in Refractory High-entropy Alloys Article

CHEN Gang, LUO Tao, SHEN Shucheng, TAO Tao, TANG Xiaotian, XUE Wei

Materials Reports 2021,35(17 ):17064 -17080. DOI:10.11896/cldb.20070306

Abstract （2656）

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Save High-entropy alloys (HEAs), also known as multi-principal component solid solution alloys, have attracted widely attention of scholars at home and abroad due to its unique alloy design concepts and excellent comprehensive properties, which have gradually become a research hot spot in the field of metal materials. Refractory high-entropy alloys (RHEAs) are thought to be a new type of superalloys designed and deve-loped based on HEAs of refractory elements. Compared with traditional high-temperature alloys, RHEAs have higher high-temperature strength, high-temperature oxidation resistance and high-temperature phase stability, implicating broad application prospects in the field of aerospace and petrochemical. Since it was proposed in 2010, RHEAs have become an important branch in the research field of HEAs.
So far, 4th, 5th, 6th periods and Ⅳ, Ⅴ, Ⅵ subgroup of 9 elements (Ti, V, Cr, Zr, Nb, Mo, Hf, Ta, W) and additional elements, such as Al, C, Co, Ni, were used as principal component of RHEAs by scholars, and formed a complex alloy system. There are more than 100 alloy systems reported, the phase structure of these alloys ranges from single-phase BCC structure to double-phase, such as BCC1+BCC2, BCC+Laves, etc., and to multi-phase structure, showing structural diversity. The microstructure of RHEAs includes dendrite, equiaxed crystal, eutectic structure or deformation twin structure, etc., and the properties determined by microstructure have its own strong points. The preparation of RHEAs first adopted melting methods, including arc melting and induction melting, which required repeated remelting under high-purity protective gas. In recent years, research has also been conducted on the preparation of RHEAs by powder metallurgy, which has obtained fine particle size and relatively uniform composition. In addition, laser cladding, magnetron sputtering, etc. are also used to prepare materials or coatings for RHEAs. It can be seen that with the deepening of research, RHEAs are constantly making new progress in the research of composition design, preparation process, phase structure and microstructure, room temperature and high temperature performance.
In this review, according to the research status in RHEAs at home and abroad in the past few years, its principal composition, phase structure and preparation method were systematically introduced, and the evolution of RHEAs properties, including density, strength and plasticity, high-temperature oxidation resistance, wear resistance and corrosion resistance, were summarized. Finally, it points out the challenges faced by RHEAs and puts forward suggestions on future research priorities.

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Research Progress on Solid Solution Strengthening of High Entropy Alloys Article

WEN Cheng, MO Wanwan, TIAN Yuwan, WANG Gui, HU Jiezhen

Materials Reports 2021,35(17 ):17081 -17089. DOI:10.11896/cldb.20070084

Abstract （1606）

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