https://dc.engconfintl.org/cgi/viewcontent.cgi?article=1032&context=superalloys_ii

A critical review of high entropy alloys and related concepts

Directly cast bulk eutectic and near-eutectic high entropy alloys with balanced strength and ductility in a wide temperature range

As human improve their ability to fabricate materials, alloys have evolved from simple to complex compositions, accordingly improving functions and performances, promoting the advancements of human civilization. In recent years, high-entropy alloys (HEAs) have attracted tremendous attention in various fields. With multiple principal components, they inherently possess unique microstructures and many impressive properties, such as high strength and hardness, excellent corrosion resistance, thermal stability, fatigue, fracture, and irradiation resistance, in terms of which they overwhelm the traditional alloys. All these properties have endowed HEAs with many promising potential applications. An in-depth understanding of the essence of HEAs is important to further developing numerous HEAs with better properties and performance in the future. In this paper, we review the recent development of HEAs, and summarize their preparation methods, composition design, phase formation and microstructures, various properties, and modeling and simulation calculations. In addition, the future trends and prospects of HEAs are put forward.

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Science and technology in high-entropy alloys

Mechanical properties of high-entropy alloys with emphasis on face-centered cubic alloys

Realizing improved strength–ductility synergy in eutectic alloys acting as in situ composite materials remains a challenge in conventional eutectic systems, which is why eutectic high-entropy alloys (EHEAs), a newly-emerging multi-principal-element eutectic category, may offer wider in situ composite possibilities. Here, we use an AlCoCrFeNi2.1 EHEA to engineer an ultrafine-grained duplex microstructure that deliberately inherits its composite lamellar nature by tailored thermo-mechanical processing to achieve property combinations which are not accessible to previously-reported reinforcement methodologies. The as-prepared samples exhibit hierarchically-structural heterogeneity due to phase decomposition, and the improved mechanical response during deformation is attributed to both a two-hierarchical constraint effect and a self-generated microcrack-arresting mechanism. This work provides a pathway for strengthening eutectic alloys and widens the design toolbox for high-performance materials based upon EHEAs. Producing in situ composite materials with superior strength and ductility has long been a challenge. Here, the authors use lamellar microstructure inherited from casting, rolling, and annealing to produce an ultrafine duplex eutectic high entropy alloy with outstanding properties.

/pdf/enhanced-strength-ductility-synergy-in-ultrafine-grained-y5tptnz2ws.pdf

Enhanced strength–ductility synergy in ultrafine-grained eutectic high-entropy alloys by inheriting microstructural lamellae

High-entropy alloys (HEAs) can have either high strength or high ductility, and a simultaneous achievement of both still constitutes a tough challenge. The inferior castability and compositional segregation of HEAs are also obstacles for their technological applications. To tackle these problems, here we proposed a novel strategy to design HEAs using the eutectic alloy concept, i.e. to achieve a microstructure composed of alternating soft fcc and hard bcc phases. As a manifestation of this concept, an AlCoCrFeNi 2.1 (atomic portion) eutectic high-entropy alloy (EHEA) was designed. The as-cast EHEA possessed a fine lamellar fcc/B2 microstructure, and showed an unprecedented combination of high tensile ductility and high fracture strength at room temperature. The excellent mechanical properties could be kept up to 700°C. This new alloy design strategy can be readily adapted to large-scale industrial production of HEAs with simultaneous high fracture strength and high ductility.

/pdf/a-promising-new-class-of-high-temperature-alloys-eutectic-v90wweyvr1.pdf

A Promising New Class of High-Temperature Alloys: Eutectic High-Entropy Alloys

Study on diffusion behavior and microstructural evolution of Al/Cu bimetal interface by synchrotron X-ray radiography

Effects of Sr on the microstructure and mechanical properties of in situ TiB2 reinforced A356 composite

Development of an 8090/3003 bimetal slab using a modified direct-chill casting process

The invention relates to a power ultrasonic device for treating high-temperature metal melt under vacuum state and a method thereof, and belongs to the field of preparation of metal materials. The method has the technical characteristics that the power ultrasonic device is used for treating the high-temperature metal melt under the vacuum state. The power ultrasonic device is characterized in that tantalum with purity being 99.98% is taken as the material of a tool head, and stable and continuous ultrasonic waves can be conducted, and the power ultrasonic device can be prevented from being corroded by high-temperature metal liquid. During the casting process, a vacuum device is adopted for protecting an ultrasonic transducer, alloy to be treated and a temperature preservation device, on one hand, the tantalum tool head can be prevented from being oxidized to deteriorate, one the other hand, the degassing effect of the ultrasonic treatment on the metal melt can be improved by virtue of the vacuum condition. For the produced alloy material, the solidification tissue is fine and compact, the distribution is uniform, and the clarifying effect is good, so that the mechanical property is greatly improved. The invention provides a new technical means for application of ultrasonic treatment of high-temperature melt in industrial production.

Tongmin Wang

Papers

A Promising New Class of High-Temperature Alloys: Eutectic High-Entropy Alloys

Study on diffusion behavior and microstructural evolution of Al/Cu bimetal interface by synchrotron X-ray radiography

Effects of Sr on the microstructure and mechanical properties of in situ TiB2 reinforced A356 composite

Development of an 8090/3003 bimetal slab using a modified direct-chill casting process

Power ultrasonic device for treating high-temperature metal melt under vacuum state and method thereof