Characterization of chemical local ordering and heterogeneity in high-entropy alloys

High-entropy alloys (HEAs) demonstrate unique mechanical properties applicable for various engineering applications. They were originally regarded as ideal solutions, where a random distribution of constituent elements is expected. However, recently, increasingly more investigations have revealed the common existence of local chemical ordering and heterogeneity in a wide range of alloy systems, which can play an important role in tuning the mechanical properties of these alloys. Therefore, the characterization of these deviations from the ideal solution assumption is necessary for the understanding of the structure–properties relationships in HEAs. This article summarizes the efforts to observe the local chemical fluctuations in HEAs with brief discussions on their effects. A short perspective for future studies is provided at the end. Graphical abstract