Nano-precipitates strengthened non-equiatomic medium-entropy alloy with outstanding tensile properties

In this work, a novel non-equiamotic Ni₄₆Cr₂₃Co₂₃Al₄Ti₄ medium-entropy alloy (MEA) strengthened by nanoscale coherent γ′ particles with L1₂ superlattice was successfully synthesized, then its microstructure, mechanical properties, strengthening and deformation mechanism were systemically investigated. Our experimental results demonstrated that this precipitation strengthened MEA exhibited outstanding strength-ductility synergy, combination a high yield strength of ~920 MPa, an ultimate tensile strength of ~1320 MPa and an excellent ductility of ~36%. The nanosized γ′ particles bought out effective precipitation strengthening in this non-equiamotic MEA, contributing a majority yield strength enhancement of ~600 MPa. For this γ′-strengthened MEA, the dominant deformation model was the stacking-faults controlled mode rather than the mechanical twin dominated mode in single-phase face-centered-cubic structure Ni₅₀Cr₂₅Co₂₅ MEA. Our work provides a further understanding of precipitate strengthening in non-equiamotic high-entropy alloys (HEAs)/MEAs.