High Entropy Alloys: An Overview on Current Developments" in the book "High Entropy Alloys: Innovations, Advances, and Applications

Abstract

High entropy alloys, being one of the advanced engineering materials, containing at least five principal elements with configurational entropy more than 1.5R, have received widespread consideration from both academia and industries due to their unique properties. Although a lot of work has been published on these materials, a thorough understanding of the basics and critical interpretation of the recent findings are still eluding researchers, which are a necessity for further advancement in high entropy alloys. Therefore, the present chapter provides a comprehensive review on current developments in high entropy alloys with a special emphasis on the thermodynamics, alloy design, and microstructure-property relationship. In terms of thermodynamic consideration for phase prediction, the importance of enthalpy and non-configurational entropy, in contrast to the earlier belief of the major role of configurational entropy in the stabilization of any phase, has been discussed in light of the recent studies. The composition of these alloys plays a pivotal role in determining the physical and mechanical properties of these alloys. Therefore, to reach to the right combination of alloying elements for desired microstructure and superior properties, various approaches are considered for designing the high entropy alloys in the past. These have been discussed in detail. As there have been a considerable number of experimental studies on high entropy alloys, a large set of data on composition, process route, and tensile properties was collected from the recent literature and was systematically analyzed to highlight the effect of individual alloying addition and processing route on microstructure evolution and tensile properties at the room, sub-zero, and high temperatures. The analysis shows exceptional tensile properties for high entropy alloy at sub-zero and high temperature, in contrast to available structural alloys.