Fe-Based Amorphous Microflakes with Deformation-Induced Nanoscale Heterogeneity Prepared by Pulse-Discharge Atomization and Ball Milling for Broadband Microwave Absorption

Fe-based amorphous alloys are attractive for microwave attenuation because they combine soft-magnetic behavior, relatively high electrical resistivity compared with compositionally similar crystalline alloys, and flexible structural design. A persistent challenge is to achieve strong attenuation and broad bandwidth at a small matching thickness without relying on complex multiphase architectures. Fe85P9C2B2Si2 amorphous powders were prepared by pulse-discharge atomization and the fine spherical fraction was subsequently flattened by controlled wet-ball milling. The atomized powders remain predominantly amorphous, whereas milling produces high-aspect-ratio microflakes together with localized approximately 5 nm band-like heterogeneous regions containing limited nanocrystalline order. Relative to the spherical powders, FP5 shows stronger dielectric and magnetic responses. At 16.9 GHz and a thickness of 1.7 mm, the attenuation constant reaches 235.9 m−1 and the normalized input-impedance magnitude is 0.999, indicating that strong intrinsic attenuation coincides with nearly ideal impedance matching. FP5 consequently exhibits a minimum reflection loss of −53.5 dB and an effective absorption bandwidth of 6.2 GHz (11.8–18.0 GHz) at 1.85 mm. The results indicate that the high-aspect-ratio morphology is the better-supported primary structural contribution to the improved absorption, while local amorphous/nanocrystalline heterogeneity may provide an additional contribution.