Effects of Silicon Content on the Properties of Gas-Atomized Fe–Si–Cr Powders

Fe-7%, 8%, 9%, and 11%Si-Cr powders were gas atomized and then annealed at 25 °C-750 °C to investigate the effects of Si content, DO
₃
phase, and B2 phase on the high-frequency permeability of the powders. The formation of the B2 phase could not be suppressed during the atomization process of all the powders. The evolution temperatures of the DO
₃
phase in the Fe-7%, 8%, and 9%Si-Cr powders as measured by X-ray diffractometer were 550 °C, 550 °C, and 450 °C, respectively. As the annealing temperature was increased, the DO
₃
phase grew rapidly, and the lattice parameters of the powders were decreased except for those of the Fe-11%Si-Cr powder. The coercivity of all powders decreased with increasing temperature; however, the coercivity of the Fe-8%, 9%Si-Cr powders increased sharply after annealing at 450 °C. Permeability decreased rapidly with increasing temperature except for the Fe-11%Si-Cr powder; thus, the highest real permeability was obtained for the as-atomized Fe-8%Si-Cr powder. The changes in the coercivity and permeability of the powders with annealing temperature could be attributed to the evolution of the DO
₃
phase, Si segregation, and changes in electrical resistivity.