Exceptional cryogenic strength and sufficient ductility of a nanotwinned high-entropy alloy fabricated by cryogenic multi-directional compression

Nanotwinned structures have been reported to produce superior mechanical properties. In this work, nanotwinned Al_0.1CoCrFeNi high-entropy alloy (HEA) was fabricated by cryogenic multi-directional compression (CMC) followed by stress-relief annealing. The nanotwinned HEA samples exhibited excellent cryogenic tensile properties with a yield strength of ∼1.2 GPa and uniform elongation of ∼27%, which is attributed to the introduction of high-density dislocations as well as hierarchical nanotwins (NTs) in the HEA samples. During the cryogenic tensile testing, more NTs were activated, increasing the possibility of dislocation and NTs interactions, further activating multiple deformation mechanisms, including the formation of stacking faults (SFs), microbands, and shear bands, thereby increasing the yield strength and maintaining a stable strain hardening ability. This strategy provides new insights into the development of high-performance HEAs applied in cryogenic environments.