Concurrently improved strength-ductility synergy and strain-hardenability in metastable face-centered cubic high-entropy alloys through C-doping

We have demonstrated that 1 at.% C-doping enhances both the strength-ductility synergy and strain-hardenability of the metastable face-centered cubic (fcc) single-phase Fe₅₀Mn₃₀Cr₁₀Si₁₀ high-entropy alloy (HEA), which exhibits transformation-induced plasticity (TRIP) effect. These enhancements result from interstitial solid solution hardening as well as a beneficial increase in fcc phase stability and stacking fault energy (SFE) due to C-doping. The increased phase stability and SFE activate deformation twinning and the formation of 9R structures, while preserving the TRIP effect. Our findings underscore C-doping as a promising strategy for designing novel high-performance metastable fcc single-phase HEAs.