Evolution of the microstructure and electromagnetic properties of Fe–Si–Al particles during post ball-milling annealing

FeSiAl alloys with a composition of Fe-9.6Si-5.4Al, also known as Sendust alloys, present the unique potential to exhibit efficient electromagnetic wave absorption (EMA) in the P-band. However, the electromagnetic properties of this type of alloy are highly sensitive to the shape, microstructure, and microchemistry, which then inspire the current research. The evolution of the microstructure/microchemistry of FeSiAl particles was systematically revealed in a single particle scale for the first time, and the resulting influence on the electromagnetic properties was investigated. Recrystallization occurs in the annealing process on FeSiAl particles and the oxide films on the surface evolve evidently when annealed in 5%H2/Ar or air, which can conduce improved electromagnetic properties. The FeSiAl particles annealed in 5%H2/Ar present efficient EMA in the P-L band while those in air contribute to high reflection loss. This work indicates the feasibility of achieving a high and adjustable EMA efficiency in the P-L band through microstructure and microchemistry tailoring.