FeCoNiCuAl high entropy alloys microwave absorbing materials: Exploring the effects of different Cu contents and annealing temperatures on electromagnetic properties

The FeCoNiCuxAl (x = 0.2–0.7) high-entropy alloy powders were synthesized by ball milling and then the prepared FeCoNiCu0.5Al powders were annealed at different temperatures (673K, 773K and 873K). The characteristics of powders were discussed, including microstructure, morphology, particle sizes, magnetic and electromagnetic properties. The crystal structures of powders are simple FCC and BCC phases with flaky microscopic morphologies. The FeCoNiCuxAl alloys with various Cu contents are soft magnetic materials, which possess high saturation magnetization and low coercivity. High conductivity and improved surface polarization with large aspect ratio of flaky powders can enhance permittivity. High saturation magnetization of soft magnetic materials can reinforce permeability. These can promote the microwave absorbing capacity of FeCoNiCuxAl alloy powders, the reflection loss (RL) of FeCoNiCuxAl alloy powders all can reach −10dB or less and the minimum RL value is −28.04 dB at Cux=0.5. Meanwhile, phases, morphology, conductivity and saturation magnetization are changed during different temperatures annealing treatment, which makes the RL values improved differently, and the minimum RL value is −40.05 dB at 673K annealing. These studies have shown that high-entropy alloys have great potential to become promising absorbers.