Abstract: This study implemented an optimized high-temperature solution treatment coupled with low-temperature aging to regulate chemical short-range ordered (SRO) structures within the CoCrNi medium-entropy alloy (MEA), and demonstrates the contribution to mechanical enhancement. Subsequently, by further combining multidirectional cryoforging (MDCF) with low-temperature aging, we engineered a multiscale microstructure concurrently containing SRO and nanotwins within coarse-grained CoCrNi MEA, achieving a remarkable improvement in strength-ductility synergy. Complementary molecular dynamics (MD) simulations and multiscale characterization techniques were employed to verify the tripartite interactions among SRO domains, twin boundaries (TBs), and dislocations, thereby elucidating the cooperative strengthening mechanisms within the SRO-nanotwin framework. The results reveal that TBs effectively obstruct dislocation motion and elevate critical stress when dislocations approach non-parallel to these interfaces. Furthermore, SRO structures enhance material strength through dual mechanisms: increasing the energy barrier for dislocation nucleation and augmenting resistance to dislocation glide. The synergistic interplay between these complementary mechanisms generates exceptional mechanical properties. Notably, specimens featuring this hierarchical architecture exhibit 53.7 % and 47.2 % enhancements in peak stress and flow stress, respectively, when benchmarked against nanocrystalline counterparts with a random solid solution (RSS) structure. This work establishes a microstructure design framework leveraging multiscale feature regulation, providing fundamental insights for the development of next-generation structural alloys. The demonstrated strategy opens novel pathways for optimizing mechanical performance through atomic-scale ordering control coupled with nanoscale twinning engineering.

Key words: Medium entropy alloy, Nanotwin network, Chemical short-range order, Strengthening mechanism