Abstract: This study investigates the development of novel high-entropy alloys (HEAs) with enhanced mechanical properties through an innovative fabrication method of direct energy deposition (DED). The focus is on the creation of metastable core-shell precipitation-strengthened HEAs that exhibit a unique multi-stage terrace-like slip wave toughening mechanism, a novel approach to improving both strength and ductility simultaneously. Mechanical testing reveals that the developed HEAs exhibit superior mechanical properties, including high yield strength, ultimate tensile strength, and exceptional ductility. The improvement in these properties is attributed to the multi-stage terrace-like slip wave toughening mechanism activated by the unique microstructural features. This toughening mechanism involves the sequential activation of slip systems, facilitated by the stress concentration around the core-shell precipitates and the subsequent propagation of slip waves across the material. The terrace-like pattern of these slip waves enhances the material's ability to deform plastically, providing a significant toughening effect while maintaining high strength levels. Furthermore, the study delves into the fundamental interactions between the microstructural elements and the deformation mechanisms. It elucidates how the core-shell precipitates and the matrix cooperate to distribute stress uniformly, delay the onset of necking, and prevent premature failure. This synergistic interaction between the microstructural features and the slip wave toughening mechanism is central to the remarkable balance of strength and ductility achieved in the HEAs. The introduction of a multi-stage terrace-like slip wave toughening mechanism offers a new pathway to designing HEAs with an exceptional amalgamation of strength and ductility.

Key words: High-entropy alloys, Direct energy deposition, Core-shell precipitates, Metastable phases, Slip wave toughening mechanism