Microstructure Evolution and Control of Mechanical Properties of AlCoCrFeNi2.1 Eutectic High-entropy Alloys Prepared by Spark Plasma Sintering

AlCoCrFeNi2.1 eutectic high-entropy alloys (EHEAs) were prepared by spark plasma sintering (SPS) technology at different sintering temperatures (900, 1 000, 1 100, 1 200 ℃) at a constant pressure of 40 MPa. The effects of temperature on the densification behavior, phase composition, macroscopic morphology and microstructure, and mechanical properties at different sections of EHEAs were studied. As the sintering temperature increases, the pore defects of the alloy gradually disappear, and the highest density can reach 99.2% (sintered at 1 200 ℃). The microstructure of SPS sintered alloy is dendrite, and its phase is composed of FCC and BCC/B2 phases, which are distributed in dendrites and interdendrites, respectively. The SPS sintered samples show anisotropy in compressive properties due to porosity effect in the low-temperature sintered state, and the anisotropy disappears with the increase of temperature. At 1 200 ℃, the strength is the highest, up to 2 690 MPa, and the plasticity reaches about 40%.