Progress in Advanced High-Entropy Alloy Design and Applications: Microstructures, Mechanical, Electrochemical and Tribological Properties

Dear Colleagues,

About twenty years ago, a non-conventional multicomponent alloy system was proposed, known as the high-entropy alloy (HEA). It has since attracted intensive interest from the materials science and engineering community. An HEA contains five or more principal elements, rather than those with one or two principal elements with other minor elements. HEAs have been extensively studied and have been demonstrated to possess many superior properties over conventional alloys. Although the HEA was initially considered to be in a state of single-phase solid solution, most HEAs actually have multi-phase microstructures, which are rather complicated. However, this also provide more opportunities for HEAs to be readily tailored for desired properties. HEAs have been found to be very promising for a wide range of applications. Significant efforts have been made to extend HEAs to various technological and industrial fields, e.g., nuclear energy, aerospace, manufacturing, mining, etc. Thus, it is important to evaluate the performance of HEAs under various operation conditions and understand the responses of HEAs to different external actions or processes. For instance, the following are representative cases that HEAs may encounter: mechanical– electrochemical attacks, wear–corrosion, fretting-hot corrosion, stress- irradiation–high-temperature synergistic attacks, erosion in aggressive environments, etc. The performance of HEAs during these processes is certainly related to their phase constituents and microstructures.

This Special Issue aims to collect research progress in these areas and provide a platform for researchers to report and share their findings, especially regarding the microstructure, mechanical and tribological properties, and performance of HEAs in different environments. Understanding the synergistic effects of different external factors would help design optimal HEAs for maximized benefits. We invite scientists and engineers to present their articles that reveal microstructural features of high- and medium-entropy alloys at various scales (such as at macro, micron, and atomic levels) and that correlate these features with the performance of the multicomponent alloys during the above-mentioned processes. All experimental and theoretical/ computational studies are welcome.

The reported studies include, but are not limited to, the following topics:

• Phase identification, crystal structures, and chemical compositions.
• Phase transformations, microstructural evolution, and control.
• Lattice defects in HEAs/MEAs (medium-entropy alloys) and their influences on the properties of the alloys.
• The design of advanced HEAs/MEAS and composites.
• Mechanical properties at different temperatures.
• Wear, corrosion, and wear–corrosion synergy at different temperatures.
• Exploring HEAs/MEAs for applications in nuclear energy, aerospace, manufacturing, mining, and others.

Dr. Anqiang He
Prof. Dr. Dongyang Li
Guest Editors

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• phase identification, crystal structures, and chemical compositions
• phase transformations, microstructural evolution, and control
• lattice defects in HEAs/MEAs (medium-entropy alloys) and their influences on the properties of the alloys
• the design of advanced HEAs/MEAS and composites
• mechanical properties at different temperatures
• wear, corrosion, and wear–corrosion synergy at different temperatures
• exploring HEAs/MEAs for applications in nuclear energy, aerospace, manufacturing, mining, and others