Strengthening methods of high-entropy alloys

High-entropy alloys (HEAs), characterized by their multi-principal element compositions, offer unprecedented opportunities to overcome the strength-ductility trade-off in structural materials. Despite their promising mechanical properties, the widespread application of HEAs remains limited by the difficulty of achieving simultaneous enhancement of strength and ductility. In response, various strengthening strategies have been adapted to enhance their mechanical performance. Due to the inherent compositional and microstructural complexity of HEAs, their strengthening mechanisms often differ from those of conventional alloys, making them a noteworthy subject for review. This review provides a comprehensive and critical assessment of recent progress in strengthening methods for HEAs, with particular emphasis on solid solution strengthening, dislocation strengthening, second-phase strengthening, grain-boundary and twin-boundary strengthening, twinning/phase transformation-induced plasticity, and hetero-deformation-induced strengthening. The interdependence between alloy composition, processing routes, microstructural evolution, and mechanical performance is systematically discussed. Special attention is given to the challenges in applying classical strengthening theories to HEAs and to the role of compositional design and thermomechanical processing in enabling tailored microstructures. Overall, this review not only clarifies the distinctive strengthening physics of HEAs and guides the design of high-performance HEAs via composition–processing–microstructure integration, but also offers transferable insights for extending and refining classical strengthening frameworks in conventional alloys.