EUROPEAN CONGRESS AND EXHIBITION ON ADVANCED MATERIALS AND PROCESSES - EUROMAT 2021

Eutectic high-entropy alloys (EHEAs), with mixed microstructures of HEA matrix and intermetallics, have advantages on flexible adjustment of microstructures. Recently, we developed a novel non-equiatomic eutectic high-entropy alloys (FeCoCrNiTaAl) with appreciable high-temperature strength. However, the intrinsically brittle Laves phase in the lamellar structure causes limited ductility at room and high temperatures. Therefore, we used direct hot extrusion of gas-atomized powder, and produced EHEA with equiaxed microstructures. The Laves lamella were disintegrated and recrystallized to be network-like, with a mean width of about 1μm. Simultaneously, the nanosized L12 phase (4–5 nm) precipitated homogeneously in the FCC matrix. The microstructure is highly stable upon annealing at 1000°C, which leads to attractive high-temperature strength. At 800C, the as-extruded alloy shows a high elongation to fracture (εF) of 33.3% and yield strength (σ0.2) of 554 MPa. Interestingly, annealing of the alloy at 1000°C for 100 h leads to a continuous/anomalous increase of the yield strength to 800 MPa, with a good enough tensile ductility of 16%. The microstructural evolution and the fracture behaviour of the EHEA were carefully characterized.