Characterisation of the Fe-10 wt% Si nanocrystalline powder obtained by mechanical alloying and annealing

Abstract

Nanocrystalline Fe-10wt% Si powders has been obtained by mechanical alloying. The synthesis conditions as well as their influence on the structural and magnetic properties of this soft magnetic alloy have been investigated in the light of several experimental techniques (X-ray diffraction, neutron diffraction, DSC, magnetic measurement, SEM). By X-ray diffraction (XRD) investigations have been highlighted that Fe-Si alloy is formed after 4h of mechanical milling and the mean crystallite size is down to 14nm (8h milled sample). The heat treatment leads to the formation of the Fe3Si compound with DO3-type superstructure for low milling times. The saturation magnetisation of the as-milled powders decreases in the first 4h of milling due to the formation of the Fe-Si alloy. The behaviour of the saturation magnetisation versus milling time and annealing was explained by the different magnetic moment of iron atoms in Fe3Si structure. The Curie temperature decreases from 770°C (the Curie temperature for pure iron) to about 650°C after 8h of milling.