Microstructure And Magnetic Properties Of Fe-based Nanocrystalline Soft Magnetic Alloy Powders Prepared By Ball Milling

Nanocrystalline soft magnetic materials have a wide application prospect in powerelectronic industry due to their excellent combination of soft magnetic properties such as high saturation magnetization,high permeability,low coercivity,low frenquency losses,near zero magnetostriction etc.Especially,the soft magnetic cores prepared by nanocrystalline powders have unique advantages in middle and high frequency fields such as switching power,mutual inductor,motor,etc.Mechanically milled nanocrystalline ribbons as a way to obtain nanocrystalline powders have been intensely studied.However,there are few reports on the nanocrystalline powders prepared by milling alloy ingots,and there is no systemic study on the powder structure,morphology,particle size and magnetic properties with various ball milling process parameters.Therefore,in this study,the Fe73.5Si13.5B9Nb3Cu1 nanocrystalline ribbons and ingots were selected as starting ball milling materials,and nanocrystalline soft magnetic alloy powders were prepared by the combination of milling and heat treatment process.The effect of milling time and heat treatment temperature on microstructure,morphology,particle size and magnetic properties has been investigated.At the same time,the difference of milling parameters and magnetic properties of nanocrystalline powders prepared by different starting materials has been compared.It is mainly including:1.When nanocrystalline ribbons were selected as starting materials,the particle size reduced and the Bs value decreased with increasing ball milling time;The fraction of amorphous phase increased gradually.When the milling time is 60 h,powders are completely transformed into amorphous state,and the average particle size and Bs value are 17 ?m and1.12 T,respectively.2.Nanocrystalline powders could be obtained by annealing amorphous powders properly.After 1 h treatment at 580 ?,the highest Bs value of 1.24 T could be obtained and the grain size of nanocrystals is about 13 nm.3.When alloy ingots were selected as starting materials,the particle size decreased with increasing ball milling time;The alloy structure underwent the transition process of crystalline — nanocrystalline+amorphous — amorphous.When the milling time is 270 h,powders are completely transformed into amorphous state,and the average particle size and Bs value are 11 ?m and 1.23 T,respectively.The nanocrystalline powders could be obtainedby annealing amorphous powders properly.After 1 h treatment at 550 ?,the highest Bs value of 1.30 T could be obtained and the grain size of nanocrystals is about 13 nm.4.Compared with milling nanocrystalline ribbons,although the preparation of powders by milling alloy ingots need more time,the nanocrystalline powders with smaller particle size and higher Bs would be obtained after heat treatment.