Achieving the excellent intermediate-temperature strength–ductility synergy in a fine-grained FeCrNi-based medium entropy alloy with heterogeneous precipitation

• A novel FeCrNiAl0.1Si0.1 medium entropy alloy achieves exceptional strength-ductility synergy at intermediate temperatures (873 K) with yield strength of 693.83 MPa, ultimate tensile strength of 817.55 MPa, and uniform elongation of 18.27%. • Heterogeneous precipitation of micron-scale σ phase at grain boundaries and nanoscale B2 phase within grains enables simultaneous strengthening and toughening across a wide temperature range. • The alloy exhibits excellent cryogenic and ambient temperature mechanical properties due to dislocation shearing of B2 phases, Orowan bypass of σ phase, and high density of nano-twins and stacking faults. • The study provides a new strategy for developing precipitation-hardened Fe-Cr-Ni austenitic alloys for high-temperature applications in nuclear and aerospace industries.