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 (Fe₆₂Ni₁₆Co₉Mn₉Ti₄)₉₇Si₃ 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)₂SiTi), 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.