ABSTRACT
High entropy alloys (HEAs) are of current interest in the materials science and engineering community. Extensive research has been carried out to understand alloy design, microstructural evolution, stability, and estimation of physical and mechanical as well as functional properties of HEAs in the last ten years. However, it is now essential to move from lab-scale to industrial-scale production to utilize these alloys for potential applications, requiring successful and repeatable synthesis of HEAs in bulk form. HEAs in bulk form can be prepared via casting, powder metallurgy (P/M), and additive manufacturing routes. With the advent of HEAs, the processing of the multicomponent and multi-principal alloys presents multiple challenges, requiring systematic investigation of the processing fundamentals and microstructural evolution. In the current chapter, fundamental issues related to processing of HEAs in the bulk form will be discussed with special emphasis on the solidification and P/M routes. During casting of multicomponent alloys, both micro- and macro-segregation plays an important role in microstructural and phase evolution. On the other hand, homogeneous and nanocrystalline microstructure can be synthesized using the P/M route in which contamination and stability of nanocrystalline phases are of paramount importance. Additive manufacturing, recently being utilized to prepare bulk HEA, has an inherent weakness of maintaining composition and phase evolution. Finally, plausible remedies to mitigate the aforementioned issues for achieving bulk HEAs by different processing routes have been discussed.
