Role of microstructural discontinuities in the soft magnetic composites with aluminium alloy addition

The paper focuses on the effect of both the aluminium alloy addition and microstructural inhomogeneties on the magnetic behaviour of soft magnetic materials tested at low frequencies. The IIPC material (base on the commercial Somaloy 1P powder) has been blended with different amounts of commercially aluminium alloy Alumix 321 (0, 5 and 10 wt %). Specimens with a different green density were obtained by pressing at a pressure in the range from 400 to 800 MPa. Different thermal treatments (in air or nitrogen at the maximum temperature of 500C for 30 min) were carried out on the evaluated systems. The microstructure investigation revealed that for materials with high aluminium alloy contents, pores are located nearby or around the aluminium alloy particles. The heat treatment regime resulted in a coarse-grained structure with a small number of inclusions within the grains and at the grain boundaries. The comparison of the results indicated that the magnetic properties were considerably dependent on the microstructural inhomogeneities.