Enhancement of magnetic properties in FeCoNiCr0.4CuX high entropy alloys through the cocktail effect for megahertz electromagnetic wave absorption

Electromagnetic wave absorption materials for megahertz (MHz) frequency range remains a key core issue that the poor effective attenuation performance and impedance mismatch. Based on previous research and theoretical analysis, an effective solution is to improve the real and imaginary parts of the complex permeability. In addition, the absorbents are also required to have excellent temperature stability and oxidation resistance due to exposure to harsh environments such as air and high temperature. Herein, the FeCoNiCr0.4CuX high entropy alloys powders (HEAs) with planar anisotropy are prepared by mechanical alloying method. Relying on the “cocktail effect” of HEAs, the addition of appropriate Cu element can increase the aspect ratio of the particles and the shape-dependent anisotropy field to further improve the permeability. Experimentally, the real part of the permeability for the FeCoNiCr0.4Cu0.2 HEAs ranges from 2.7 to 7.5 and the imaginary part of the permeability can reach 2.7 in the MHz frequency range. The maximum reflection loss can reach −33.6 dB at 484 MHz and the effective absorption bandwidth (reflection loss<−10 dB) can almost cover the entire MHz frequency range. Furthermore, the FeCoNiCr0.4Cu0.2 HEAs have stable electromagnetic wave absorption performance and superior oxidation resistance with increasing temperature. This research exploits the characteristics of HEAs to further break the inherent magnetic limit by adjusting the morphology and provides a new pathway for solving the matter of MHz electromagnetic wave absorption.