Tomsk Scientific Center of SB RAS has summarized research in high-entropy alloys over the past 50 years

A review of progress and obstacles with high-entropy alloys as structural materials, prepared by scientists Mikhail Slobodyan, Evgeny Pesterev, and Alexey Markov (Tomsk Scientific Centre of SB RAS), has been published in Materials Today Communication (Elsevier BV, Netherlands). A comprehensive 80-page review with over 500 references, covering all major recent works, was published within a month and a half after submission to the journal.

“The main objective of our review is to make a complete inventory of the achievements, controversies and gaps in the knowledge of high-entropy alloys (HEA), which will allow us to highlight the promising directions for further research on this topic,” – the authors explain.

HEAs are defined as solid solution alloys that comprise at least five principal elements in equal or near equal atomic concentration. First produced in 2004, these alloys have been the subject of research for many years since the late 1960s. During this period, several thousand scientific papers have been published in this field, and the most important results have been summarized in more than one hundred reviews and monographs.

In conventional alloys, a basic element of the crystal lattice is iron, nickel, or aluminium. In HEA, the crystal lattice is composed of atoms of different elements and is highly distorted. These alloys have superior physical properties, such as strength, ductility, high resistance to mechanical stress, chemical, thermal and radiation effects, etc. Scientists around the world are searching for optimal compositions of these materials and technologies to produce them.

However, there are sceptical voices in the scientific literature that question the exceptional properties of HEA. This view is based on the fact that these alloys have not been used in industry for two decades. A comparison of the many pros and cons formed the basis of the review concept.

Tomsk’s scientists have evaluated the prospects of replacing metals and alloys currently used in nuclear power and medicine with HEA. They discussed the possibilities of surface treatment using both traditional methods and high-energy sources, including glow discharge plasma, lasers and electron beams. The review concluded that considerable progress has been made in the last two decades in the development of computational modelling and experimental methods in materials science. However, despite this progress, the prospects for using HEA, particularly at high operating temperatures, do not look promising for the future.

The authors concluded by suggesting the unification of terminology, the standardization of test methods and the creation of a global test database that would trace the interdependencies between the composition, structure and properties of such materials and their treatment methods.