A cost-effective cryogenic high-entropy alloy with high strength-ductility synergy and strain hardenability

High entropy alloys (HEAs) with a face-centred cubic (FCC) matrix usually exhibit exceptional cryogenic me-chanical properties. However, their industrial applications are limited due to their high cost resulted from the use of expensive elements, including Co, V, etc. In this work, a cost-effective HEA, Fe35Ni35Cr20Mo5Al5, with a single FCC matrix is developed, aiming at enhancing the application potential of cryogenic FCC-HEAs. The HEA showed a temperature-dependent tensile properties. Its yield strength and tensile strength were increased from-302 MPa to 455 MPa and from-673 to-952 MPa with ductility increased from-68% to-84% when the tem-perature was decreased from 298 K to 77 K. In particular, the steady-state strain hardening rate was-2 GPa at 77 K, which is twice of that at 298 K. Compared with previously reported cryogenic HEAs, the new alloy has a relatively low raw materials cost but possesses a superior strain hardening capacity and exceptional strength -ductility synergy at 77 K. Its excellent property is ascribed to the formation of a complicated nanoscale twin network and its extensive interaction with dislocations. The combination of relatively low raw materials cost and superior cryogenic mechanical properties make this HEA a promising material candidate for cryogenic applications.