Metastable High Entropy Alloys
High entropy alloys (HEAs), multi-principal-element alloys, or complex concentrated alloys (alloys made up of approximately equal proportions of usually five or more elements) were initially studied for their tolerance to high temperatures and pressures meeting the need for advanced materials under extreme conditions, the focus being the formation of a single phase. More recently, metastability in high entropy alloys has become an area of active research, since such metastability, both compositional as well as structural, is inherent in many HEAs. Further, this inherent metastability in HEAs can be designed and exploited for achieving enhanced mechanical and functional properties, and forms the basis of this special topic collection in APL. Compositional metastability in HEAs typically leads to decomposition of the complex concentrated solid solution via thermally activated processes (e.g. diffusion) – resulting in the precipitation of second (or more) phases and the formation of a complex multi-phase microstructure. Structural metastability in HEAs often leads to stress-induced martensitic transformation and deformation twinning. Such phenomena lead to transformation induced plasticity (TRIP) and twinning induced plasticity (TWIP) in HEAs.
Guest Editor: Yandong Wang, Rajarshi Banerjee, Levente Vitos, and Xiongjun Liu