Abstract:

High-entropy alloys (HEAs) show excellent prospects in microwave absorbing materials due to their designable composition and variable electromagnetic properties. In this work, FeCoCrAl_0.4V_x HEAs with body-centered cubic (BCC) single-phase solid solution structure were prepared by mechanical alloying and heat treatment. By varying the content of vanadium (V), the grain size, lattice constant, crystallinity, particle size, and microscopic morphology can be effectively adjusted, thereby enabling the optimization of their electromagnetic properties and microwave absorption performance. Doping a small amount of V element can refine the BCC grains, regulate the particle size, and enhance the electrical conductivity, which significantly improves the polarization relaxation, conduction loss, and eddy current loss of HEAs. In addition, the increased crystallinity and reduced lattice defects can enhance natural resonance loss at a high frequency (GHz), which will contribute to the improvement of impedance matching and electromagnetic attenuation. The annealed FeCoCrAl_0.4V_0.2 HEAs exhibit excellent wave absorption properties, achieving a maximum reflection loss of −44.3 dB at 1.8 mm thickness and an effective absorption bandwidth of 4.0 GHz at 1.2 mm, respectively. This study provides a new strategy for developing lightweight and high-performance high-entropy alloys microwave absorbing materials.

Key words: High-entropy alloys, Microwave absorbing materials, Refine grains, Impedance matching