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 Fe
_81.4+x
Si
_17-x
Cr
_1.6
(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 Fe
_81.4+x
Si
_17-x
Cr
_1.6
(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 (μ'') 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 Fe
_85.4
Si
₁₃
Cr
_1.6
alloy powders with the increase of milling time, the peaks of μ'' transfer to the higher frequency, while the values of μ'' 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.