Effects of Ordering on the Magnetic Properties of Gas-Atomized Fe–Si–Cr Powders

Fe-9%Si-2%Cr powder was gas-atomized and then annealed in order to investigate the effects of DO
₃
and B2 ordered phases on high-frequency permeability of the powder. The B2 phase is formed during the atomization process. The DO
₃
phase began to form at 450 °C and grew rapidly when annealed at higher temperature as confirmed by X-ray diffractometer, whereas the existence of the DO
₃
phase in the as-atomized powder could be confirmed by electron transmission microscope. With the increase in the temperature, the average lattice parameter and the coercivity decreased. There was an abrupt increment of the coercivity in the powder annealed at 450 °C. Highest permeability could be obtained in the powder annealed at a relative low temperature of 150 °C and then the permeability real decreased with the temperature. The behavior of the coercivity and the permeability with the temperature could be successfully explained by the formation of the DO
₃
ordered phase and the change of the electrical resistivity.