Dear Colleagues,

The goal of this Special Issue is to discuss major materials issues for complex concentrated alloys (CCAs) and high entropy alloys (HEAs), from property-targeted design to process optimization, from structures to properties, and from the fundamental science to viable industrial applications. CCAs have been reported to have useful performances, including great toughness, high-temperature strength, corrosion resistance, as well as a good irradiation resistance. In addition, the concept of CCAs shifts the focus away from the corners of alloy phase diagrams toward their centers, vastly increasing the number of possible alloy systems with an unexplored property realm. Thus, CCAs have attracted worldwide attention as a new generation of alloys to resolve the challenges of modern industries in the fields of transportation, energy, safety, and infrastructure with remarkable properties never seen before.

Much of the interest in CCAs and HEAs is predicated on the belief that the maximized chemical complexity with multiprincipal elements would produce profound intrinsic core properties, such as the high entropy effect, the lattice distortion effect, the sluggish diffusion effect, the solid-solution strengthening effect, and the cocktail effect. Thus, early design strategies focused on increasing the number of principal elements and the configurational entropy to maximize the benefits of chemical complexity. Recently, however, several studies have shown that the nature of elements is more important for the complexity-related properties than their mere numbers. This introduces a new challenge, because not every combination of elements would be successful in achieving beneficial properties. As a result, the advantage of so many degrees of freedom for alloy design of CCAs is diminished by a lack of mixing rules, rendering alloy design an empirical try-and-error undertaking. Therefore, to make a useful guide for the new CCA and HEA design, careful guidelines are required to consider the atomic environments of CCAs in a physically meaningful way. In this Special Issue, we hope to present the design guidelines of new CCAs and HEAs, as well as highlight some challenging fundamental and application issues for their properties.

Prof. Dr. Eun Soo Park
Dr. Hyunseok Oh
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. Metals 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.

• High-entropy and complex-concentrated alloys
• Material fabrication and processing
• Theoretical modeling and simulation
• Properties (mechanical, physical, magnetic, electric, thermal, and corrosion)
• Industrial application