Magnetic properties of porous iron compacts

Magnetic hysteresis measurements, magnetoacoustic emission, and the Barkhausen effect have been used to investigate the magnetic properties of six porous iron compacts with porosities in the range 0.3–6.2% and pore sizes in the range 1.6–13.2 µm. Coercivity and maximum permeability varied with pore size, showing respectively a maximum and a minimum for pore areas in the range 50–100 (µm)², corresponding to pore diameters 8–11 µm. Significant correlations were found between several of the magnetic parameters including a fundamental relationship between coercivity, initial permeability, and maximum differential permeability. There were also indications of a correlation between magnetic properties and the initial molding pressure, although these were not conclusive. However, none of the magnetic properties was found to vary in a progressive manner with percentage porosity, although it is conceivable that if all other variables, such as pore size and grain size, remained constant, that changes in magnetic properties with porosity could be detected from magnetic measurements.