A novel high-entropy alloy with multi-scale precipitates and excellent mechanical properties fabricated by spark plasma sintering

Body-centered-cubic (BCC) high entropy alloys (HEAs) usually exhibit high strength but poor ductility. To overcome such strength-ductility trade-off, a novel (FeCr)₄₅(AlNi)₅₀Co₅ HEA was presented in this paper, which was designed and fabricated with mechanical alloying (MA) followed by spark plasma sintering (SPS), and has a heterogeneous microstructure with multi-scale precipitates. Electron microscopy characterization revealed that the sizes of the precipitates range from nano (<300 nm), sub-micron (300～800 nm) to micron (>1 μm). The bulk HEA exhibits excellent mechanical properties, of which the compressive yield strength, fracture strength, and plasticity at room temperature can reach 1508 MPa, 3106 MPa and 30.4 %, respectively, which are much higher than that of most HEAs prepared by Powder Metallurgy reported in the literatures, suggesting that the HEA developed is highly promising for engineering applications. The excellent mechanical properties of the bulk HEA can be attributed to that the multi-scale precipitates are fully coherent with the matrix, which could reduce the misfit strain at the interface, and relieve the stress concentration during deformation.