Ultrahigh-strength heterostructure eutectic high-entropy alloys with multiple strengthening mechanisms at cryogenic temperature

Eutectic high-entropy alloys (EHEAs) have attracted considerable attention owing to their remarkable strength-ductility synergy over a wide temperature range. However, the mechanisms governing their exceptional cryogenic mechanical performance remain insufficiently understood. Here, a heterogeneous dual-phase microstructure was successfully engineered in an Al 4.25 CoCrFe 5 Ni 12.25 V 1.5 EHEA through thermomechanical processing. An outstanding yield strength of ∼1.85 GPa, an excellent ultimate tensile strength of 2.06 GPa and a fracture elongation of 6.9% at 77 K were achieved. The high strength at 298 K primarily originates from grain-boundary, precipitation, and lattice friction strengthening. At 77 K, the reduced stacking fault energy promotes the formation of stacking faults and deformation twins. Consequently, the exceptional cryogenic mechanical performance is attributed to the synergistic contributions of these intrinsic and cryogenic-induced strengthening mechanisms. These findings offer guidance for the design of cryogenic structural materials.