Discovery of a novel low-cost medium-entropy stainless steel with exceptional mechanical behavior over a wide temperature range

Abstract

Stainless steels exhibit strength-ductility trade-off and insufficient elevated-temperature strength. Here, we report a novel low-cost, cobalt-free, Fe₄₇Cr₁₆Ni₂₆Ti₆Al₅ medium-entropy stainless steel (MESS) strengthened by high-density coherent L1₂ nanoprecipitates (NPs) with a high ultimate tensile strength of 1.35 GPa and a total elongation of 36% at room temperature (RT). The ductile L1₂ NPs working together with the dynamic refinement of the deformation substructures cause an excellent work-hardening ability. Furthermore, the MESS maintains a high yield strength of ∼0.8 GPa at 700°C, which is not only better than many iron-based superalloys and stainless steels but also comparable to some nickel-based superalloys. The steady-state creep rates at 750°C are at least two orders of magnitude lower than those of some nickel-based superalloys and heat-resistant steels. The excellent creep resistance is achieved via the strong interactions between sliding dislocations and stable L1₂ NPs, which effectively impede the movement of dislocations.