Abstract:The essence of absorbing materials research is to adjust the composition and structure of the material to control its complex permittivity and complex permeability, so that as many electromagnetic waves as possible can enter the absorbing material, to enhance the absorption capacity of the material to electromagnetic waves. In this study, FeNiCrAl0.4Cux (x = 0.2, 0.4, 0.6, 0.8, 1.0; mole ratio) high-entropy alloy wave-absorbing materials with soft magnetic properties were prepared by high-energy ball milling method, and the ball-milled powders showed irregular flake structure. The experimental results showed that adjusting the content of Cu elements could improve the aspect ratio and shape-related anisotropy of the powder particles and promote the surface polarization, thus improving the complex dielectric constant and complex permeability of the powder and further enhancing the electromagnetic loss capability. As the molar ratio of Cu content increased from 0.2 to 1.0, the impedance matching of the powder gradually improved and the attenuation coefficient and reflection loss are enhanced, when x = 1.0, the powder had the highest attenuation coefficient and the lowest reflection loss of -23.74 dB, with a thickness of 2.0 mm. It was noteworthy that by adjusting the thickness of the material, the effective absorption bandwidth (reflection loss <-10 dB) of FeNiCrAl0.4Cux could cover almost the whole C-Ku (4~18 GHz) band. This study was important to realize the broadband absorption of high-entropy alloy absorbing materials.