EFFECTS OF MILLING TIME, Si CONTENT AND HEAT TREATMENT ON MICROSTRUCTURE AND MAGNETIC PROPERTIES OF MECHANICALLY ALLOYED Fe-Si POWDERS

摘要

In this study, the effects of milling time, chemical composition and heat treatment on microstructure and magnetic properties of nanocrystalline Fe-Si (6.5-25 at. percent Si) alloys prepared by mechanical alloying have been investigated. The results show that increasing the milling time or the Si content, decreases the lattice parameter and increases the internal microstrain. The prepared powders mainly consist of micron-sized particles with an average grain size of less than 20 nm. The specific saturation magnetization values are slightly less than those of single crystal or conventional Fe-Si alloys and decrease as Si content increases. The coercive force values of the nanocrystalline as-milled powders are much higher than those of corresponding Fe-Si bulk alloys with a minimum at 13.5 at. percent Si. The values of coercive force decreased after annealing but it seams that the residual strain developed during milling is not the major contributing factor to the higher values of coercive force in the mechanically alloyed powders and nanocrystals behave as single-domain particles without exchange interaction between them.