Abstract: In the present study, a face-centered cubic non-equiatomic Cr₂₆Mn₂₀Fe₂₀Co₂₀Ni₁₄ high-entropy alloy (HEA) with a low stacking fault energy of 17.6 mJ m^-2 was prepared by vacuum induction melting, forging and annealing processes. The recrystallized sample is revealed to exhibit an excellent combination of strength and ductility over a wide temperature range of 4.2-293 K. With decreasing temperature from 293 to 77 K, the ductility and ultimate tensile strength (UTS) gradually increase by 30% to 95% and 137% to 1020 MPa, respectively. At the lowest temperature of 4.2 K, the ductility keeps 65% and the UTS increases by 200% to 1300 MPa, which exceed those published in the literature, including conventional 300 series stainless steels. Detailed microstructural analyses of this alloy reveal a change of deformation mechanisms from dislocation slip and nano-twinning at 293 K to nano-phase transformation at 4.2 K. The cooperation and competition of multiple nano-twinning and nano-phase transformation are responsible for the superior tensile properties at cryogenic temperatures. Our study provides experimental evidence for potential cryogenic applications of HEAs.

Key words: High-entropy alloys, Strength and ductility, Cryogenic temperature, Twinning, Phase transformation