Abstract: As-cast alloys often require complex thermomechanical processing to obtain a hierarchical structure to achieve a good combination of strength and ductility. Here in this work, a novel hierarchical Fe₂₇ Ni₃₅ Cr_18.25 Al_13.75 Co₂ Ti₂ Mo₂ high-entropy alloy (HEA) with ultra-high tensile strength and excellent ductility was fabricated by direct casting. The as-cast alloy exhibits hierarchical structure with an ul-trafine lamellar microstructure (ULM), ultrafine rhombus microstructure (URM), ultrafine vermicular mi-crostructure (UVM), nanosized precipitates and spinodal decomposition (SP) that develops during casting and cooling. The incompatibility of face-centered cubic (FCC) and body-centered cubic (BCC) phases in the deformation process leads to heterogeneous deformation-induced (HDI) hardening, which brings the alloy a tensile yield strength (YS) of ∼1056 MPa, an ultimate tensile strength (UTS) of ∼1526 MPa and a total elongation (El) of ∼15.6%. Additionally, the numerous interfaces generated by the hierarchical structure absorb the energy during deformation, effectively retarding the dislocation motion and causing strong work-hardening.

Key words: Direct casting, High-entropy alloy, Hierarchical microstructure, Mechanical properties