The goal of this paper is to make an overview of high entropy alloys. First it explains definition of high entropy alloy and the thermodynamics of its creation. As it is evident from their name HEAs have high entropy compared to conventional alloys. High entropy is assumed to stabilize HEA at high temperatures and cause HEA to form one phase solid solution instead of multiple phases. In addition to high entropy effect the paper discusses three other key mechanisms which are thought to give HEAs exceptional mechanical properties. These are lattice distortion, slow diffusion, and cocktail effect. Lattice distortion is a consequence of different sizes of atoms which make up a certain HEA. Slow diffusion and cocktail effect are both caused by interactions between different atoms. Cocktail effect encompasses all properties of HEA which arise from individual elements and their mutual interactions. However, all four mechanisms are either not yet proven or not present to greater extent than in conventional alloys. Research suggests that properties of HEAs are not the result of their unique and new mechanisms but rather already existing ones. Therefore, microstructures of HEAs and their effect on mechanical properties are also described. Along with mechanical properties the paper explores functional properties, namely biocompatibility and catalytic activity. Some common methods of synthesis are also presented together with their advantages and disadvantages. Finally, the paper lists some possible applications of HEAs based on their mechanical and functional properties.
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