Tunable electromagnetic properties via dealloying in FeCoNiCuAl high-entropy alloys for efficient electromagnetic-wave absorption

High-entropy alloys (HEAs), especially the FeCoNi-based HEAs with magnetic loss and dielectric loss, have attracted considerable attention in the field of electromagnetic-wave absorption (EMA). However, improper electromagnetic parameters of HEAs led to impedance mismatching, which considerably reduced its electromagnetic-wave absorbing efficiency. Dealloying in HEAs is an available approach to optimizing electromagnetic properties owing to its function of component tailoring and surface modification. Herein, FeCoNiCuAl HEAs were prepared by the high-energy balling method, and then, the as-milled powders were dealloyed in KOH solution with different concentrations. Undergoing the dealloying process, Al contents in FeCoNiCuAl HEAs decreased, while the surface area increased, which efficiently optimized impedance matching and promoted surface polarization loss. Profiting from these merits, samples A02 and A06 exhibit excellent EMA performance, with strong absorptions of -56.04 dB at 13.01 GHz and -56.12 dB at 6.88 GHz, corresponding to bandwidths of 3.29 GHz (1.69 mm) and 2.88 GHz (1.69 mm), respectively.