Direct-casting induced micro-cellular segregation and supranano precipitates enhance strength-ductility in Co-free medium-entropy alloys

Overcoming the strength-ductility trade-off in alloys without complex post-processing remains a critical challenge. Here, we designed a hierarchical heterostructure of micro-cellular segregation (MCS) and supranano precipitates (SNPs) in the directly cast medium-entropy alloy (MEA), achieving higher strength without a significant loss of plasticity. This MCS-SNP alloy exhibits a superior combination of tensile strength (~922 MPa) and elongation (~32%) compared with most traditional as-cast face-centered cubic (FCC) alloys. The MCS impedes the movement of the slip bands and maintains the flow stress in the work-hardening process. The SNPs enhance the pinning effect of dislocations, providing an additional source of work hardening together with microbands. The synergistic effect of MCS and SNP generates significant back stress at both micro and nano scales. The findings of this study provide a promising strategy for designing high-performance casting alloys with integrated microscale cellular segregation and supranano precipitate structures.