Architecturing unique microstructures in high-entropy alloys via compositional complexity for superior mechanical performance: a critical review

Departing from the initial paradigm of single-phase solid-solutions, high-entropy alloys (HEAs) have evolved to actively exploit their inherent compositional complexity as a strategic lever for microstructural design. This review synthesizes recent advances by categorizing and analyzing three distinct classes of microstructures uniquely enabled by this chemical complexity: unique solidification microstructures (eutectic, peritectic, eutectoid), multi-scale solid-state precipitates, and chemical short-range order (CSRO) configurations. Crucially, we elucidate not only the individual formation mechanisms of these microstructures but also their cross-coupling interactions across multiple length scales. Furthermore, we detail how these distinct structural features interplay with fundamental deformation mechanisms to achieve unprecedented mechanical properties. By establishing explicit composition-microstructure-property linkages, this work provides a targeted framework for leveraging chemical complexity, moving beyond empirical exploration toward the rational design of next-generation HEAs with tailored hierarchical architectures and superior performance.