Studies on Magnetic Properties and Ball-Milling Process of Fe–Si–Cr Powders

Flake-shaped Fe–Si–Cr alloy powders were prepared by crushing alloy ingots and the ball milling method. Magnetic properties of Fe–Si–Cr alloy powders with the nominal compositions of Fe81.4+ x Si17– x Cr1.6 ( $x=0,2,4$ , and 6) and the different values of milling time (0 to 120 h) were investigated. A scanning electron microscope, X-ray diffraction, and a vibrating samples magnetometer were used to characterize Fe–Si–Cr alloy powders. It is observed that, with the increase of parameter $x$ , the permeability of Fe81.4+ x Si17– x Cr1.6 ( $x=0$ , 2, 4, and 6) powders first increases and then decreases in 0.5–2 GHz, meanwhile the peaks of the imaginary part of the magnetic permeability ( $\mu ''$ ) transfer to the lower frequency in 0.5–6 GHz. The saturation magnetic ( $M_{S})$ and the coercivity ( $H_{C})$ were also investigated. The value of $M_{S}$ increases from 110 emu/g ( $x=0$ ) to 148 emu/g ( $x=6$ ), while the value of $H_{C}$ changes in the opposite trend from 30.7 Oe ( $x=0$ ) to 25.5 Oe ( $x=6$ ). For Fe85.4Si13Cr1.6 alloy powders with the increase of milling time, the peaks of $\mu ''$ transfer to the higher frequency, while the values of $\mu ''$ first increase and then decrease in 0.5–10 GHz. We attributed this to the change of the aspect ratio. A large aspect ratio increases planar anisotropy, which can enhance the magnetic permeability of the material. It is observed that the imaginary part of the magnetic permeability is 3.91 with $x=4$ and milling time $= 48$ h at 1.1 GHz.