Microstructure and properties of heat treated iron powder compacts intended for ac soft magnetic applications

This paper describes the effect of heat treatments on the microstructure an d properties of iron powder specimens intended for ac soft magnetic applica tions at 60 Hz. The specimens were fabricated by compacting iron powder lub ricant (zinc stearate) mixes and heat treating the compacted specimens at 4 50-550 degreesC in nitrogen. The microstructure and chemical characteristic s of particle interfaces (X-ray photoelectron spectrometry) and the presenc e of microstrains (neutron diffraction) were correlated with the electrical and magnetic properties of the material, During the heat treatments (450-5 50 degreesC), lubricant burns out and iron oxide contacts are created at pa rticle interfaces (thermal oxidation bonding). Iron powder oxidation, which depends on the heat treatment temperature, reduces the electrical resistiv ity of the material and affects eddy current loss, The heat treatments modi fy the microstrains in the specimens and allow reduction of the hysteresis portion of the magnetic loss, MST/4437.