High Entropy Alloys for Energy Conversion and Storage: A Review of Grain Boundary Wetting Phenomena

Abstract

The multicomponent alloys with nearly equal concentration of components, also known as high entropy alloys (HEAs), were first proposed 22 years ago. The HEAs quickly became very important in materials science due to their unique properties. Nowadays, the HEAs are frequently used in energy conversion and storage applications. HEAs can consist of five, six or more components. Plasma cladding permits coating of the large surfaces of cheap substrates with (often expensive) HEAs and to enlarge, in such a way, their application area. The large-area coatings deposited by plasma cladding possess multiple advantages such as low thermal distortion, very high energy density, as well as low dilution of the substrate material. Plasma cladding ensures good metallurgical bonding between coating and substrate. The costs of operation and equipment are also very attractive. During plasma cladding, the mixed powders are blown by carrier gas into a plasma torch or are positioned on a substrate. This powder mixture is then melted in or under the plasma torch. The plasma torch, in turn, sequentially scans the substrate. After finalizing the crystallization process, the solid polycrystal appears which contains few residual melts. This remaining melt can completely or incompletely wet the grain boundaries (GBs) in solid phase of the polycrystal. These completely or incompletely wetted GBs can strongly influence the microstructure of HEA coatings and their morphology. In this review we analyze the GB wetting HEAs containing one phase in HEAs with two, three and more phases, as well as in HEAs reinforced with particles of carbides, nitrides, borides, or oxides. We also analyze the microstructure of the rather thick coatings after plasma cladding after additional laser remelting and observe how GB wetting changes over their thickness.

Effect of Cu on microstructure and properties of Co2CrFeNiMnCux high-entropy alloy coatings prepared by laser cladding

“…However, different coating preparation methods led to some variations in phase structures and microstructures of HEAs. 14,15 Presently, the main methods for preparing HEACs included thermal spray, 16 electrochemical deposition, 17 magnetron sputtering, 18 laser cladding, 19 and plasma spraying. 20 Dang et al 21 prepared CoCrFeNiMn HEAC films by high vacuum radio frequency (RF) magnetron sputtering technique.…”

Phase Transformations Caused by Heat Treatment and High-Pressure Torsion in TiZrHfMoCrCo Alloy

“…The TiZrHfMoCrCo alloy studied in this paper belongs to promising biomaterials, its biocompatibility is comparable to commercially pure titanium, which is used for orthopedic implants. Detailed reviews on HEAs can be found in References [ 17 , 18 , 19 ].…”

Influence of Heat Treatment and High-Pressure Torsion on Phase Transformations in TiZrHfMoCr High-Entropy Alloy

“…Since the high-entropy alloys (HEAs) were originally proposed by Cantor et al [1] and Yeh et al [2], there has been a growing interest in these multicomponent metallic materials. With a wide range of chemical compositions available, HEAs exhibit a variety of phase transformations, mechanical properties, and microstructural types, leading to a wealth of research publications, including numerous reviews [3][4][5][6]. Typically, HEAs consist of five or more components, with proportions ranging from 5 to 35 at.%.…”