Heating rate dependence of magnetic properties for Fe-based nanocrystalline alloys

Influence of heating rate on magnetic properties of Fe(72.7)Cu(1)Nb(2)V(1.8)Si(13.5)Bg and Fe73.5Cu1Nb3Si13.5B9 alloys in nanocrystallization at 550 degrees C was investigated. The results of magnetic measurements showed that the effect of heating rate on permeability was significant, the initial permeability mu(i) was significantly increased by quick heating. For Fe72.7Cu1Nb2V1.8Si13.5B9 alloy, when heating rate was raised from 2 degrees C/min to 260 degrees C/min, mu(i) was increased from 42 000 to 81 000; for Fe73.5Cu1Nb3Si13.5B9 alloy, when heating rate was raised from 0.5 degrees C/min to 260 degrees C/min, mu(i) was increased from 26 000 to 92 000. It was found that the grain size D was decreased by quick heating. For Fe72.7Cu1Nb2V1.8Si13.5B9 alloy, when heating rate was raised from 2 degrees C/min to 260 degrees C/min, D was decreased from 14.6 to 13.1 nm; for Fe73.5Cu1Nb3Si13.5B9 alloy, when heating rate was raised from 0.5 degrees C/min to degrees 260C/min, D was decreased from 13.1 to 10.6 nm. This suggested that the effect of heating rate on permeability was caused mainly by the changes of grain size. The plot of grain size and mu(i) showed that mu(i) proportional to D-6. The dependence of nucleation frequency and growth rate on heating rate are discussed.