Fe-based high-entropy alloy with excellent mechanical properties enabled by nanosized precipitates and heterogeneous grain distribution

Abstract

High-entropy alloys (HEAs) consisting of CoCrFeNiAlTi systems, with a face-centered cubic (FCC) matrix reinforced by ordered L12 precipitates, have demonstrated exceptional strength-ductility combinations. However, the current compositional design of HEAs heavily relies on high Ni and Co contents, compromising the balance between properties and cost. Thus, it is crucial to optimize the cost-performance trade-off by fine-tuning the range of Fe, Co, and Ni, while maintaining excellent strength-ductility combination. In this study, we propose a novel Fe-based HEA with nanosized precipitates and a heterogeneous grain distribution, achieving a strength-ductility combination comparable to state-of-the-art Ni- or Co-based HEAs. The alloy benefits from both precipitation hardening and hetero-deformation-induced strengthening attributed to the heterogeneous grain distribution, resulting in excellent yield strength of 1433 MPa, tensile strength of 1599 MPa, and ductility of 22%. The microstructural evolution and its influence on mechanical properties are unraveled with respect to the observation of precipitate-dislocation interaction and hetero-deformation-induced stress (HDI stress) evaluation. This study suggests that the challenge of balancing properties and cost can be addressed through optimized compositional and microstructural design.