Enhanced cryogenic tensile properties in a Fe-high-entropy alloy

Face-centered cubic (FCC) high-entropy alloys (HEAs) typically exhibit excellent ductility and are expected to be used in cryogenic engineering applications. However, their moderate yield strength at cryogenic temperatures (typically below 1 GPa) and the high cost of the alloys limit their application. In this paper, we report a (Fe 62 Ni 16 Co 9 Mn 9 Ti 4 ) 97 Si 3 Fe-high-entropy alloy (Fe-HEA) with excellent cryogenic tensile strength (yield strength and ultimate tensile strength of 1325 MPa and 1446 MPa, respectively) and ductility (uniform elongation of 20 %). The ultrahigh cryogenic yield strength and uniform elongation of our alloy stem primarily from superior work-hardening and strain-hardening capabilities induced by the heterogeneous structures of bimodal grains and dual phase, FCC → BCC / HCP martensitic transformation , ductile nano-precipitates ((Fe, Ni) 2 SiTi), nano-twins, stacking faults , and Lomer-Cottrell locks. The findings of this study provide new insights for developing Fe-HEAs with a good combination of yield strength and ductility at cryogenic temperatures. • Developed a Fe-HEA exhibiting outstanding cryogenic yield strength and ductility synergy. • Revealed the mechanical response and strain-hardening behavior at cryogenic temperature. • Clarified the impact of Si addition on the heterogeneous structure and cryogenic tensile properties.