About the book
High-entropy alloy (HEA) is a new class of materials characterized by the crystal in which more than five elements with the atomic fraction of each component between 5% and 35% randomly occupy one crystallographic site. The concept of HEA has initially developed in the single-site crystal structures such as face-centered-cubic (fcc), body-centered-cubic (bcc), and hexagonal-closed packing (hcp), however, is now adopted in many multi-site alloys (multi-site HEAs). Due to the severe lattice distortion effect, many fcc or bcc HEAs show superior mechanical properties, which attract researchers all over the world. The superior mechanical properties result from the cocktail effect, which means an enhancement of property beyond the simple mixture of those of constituent elements. The cocktail effect is also observed in a multi-site HEA: for example, outstanding thermal stability or enhancement of magnetic frustration in a high-entropy alloyed oxide. Due to the massive elemental combination of the HEA system, there are unlimited possibilities of finding new phenomena in the materials research on HEAs. The conventional metallurgical study for bulk HEA is significant steady work in not only the single-phase sample but also the multiphase sample such as eutectic HEA. In addition, fabrications of thin film and nanocrystalline samples of well-known HEAs are important works. It is widely accepted that first-principle calculations, machine learning, and CALPHAD (calculation of phase diagram) are powerful methods for screening new compounds. Very interesting topics concerning the mechanical, physical and chemical properties are new HEAs showing high strength, high ductility, good thermal stability, refractory, superconductivity, exotic magnetism, and so on. The topics concerning applications are also interesting, for example, coating against the corrosion, biomaterials, catalysts, shape memory alloys, magnetic refrigeration materials, and so on.
This book intends to provide the reader with a comprehensive overview of the frontier of materials research, exotic properties (mechanical, physical, chemical et al.), and exciting applications in HEAs.