Influence of heating rate on magnetic properties for Fe72.7Cu1Nb2V1.8Si13.5B9 alloy and Fe73.5Cu1Nb3Si13.5B9 alloy in nanocrystallization at 550℃ was investigated.Magnetic measurements showed that the effect of heating rate on permeability was significant,the initial permeability μi was significantly increased by quick heating.For Fe72.7Cu1Nb2V1.8Si13.5B9 alloy,when heating rate was raised from 2℃/min to 260℃/min, μi was increased from 42000 to 81000; for Fe73.5Cu1Nb3Si13.5B9 alloy,when heating rate was raised from 0.5℃/min to 260℃/min,μi was increased from 26000 to 92000.It was found that the grain size was decreased by quick heating.For Fe72.7Cu1Nb2V1.8Si13.5B9 alloy,when heating rate was raised from 2℃/min to 260℃/min,the grain size was decreased from 14.6nm to 13.1nm;for Fe73.5Cu1Nb3Si13.5B9 alloy,when heating rate was raised from 0.5℃/min to 260℃/min,the grain size was decreased from 13.1nm to 10.6nm.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 μi showed that μi∝D-6 ,where D is the average size of the grains.The nucleation frequency and growth rate of α-Fe(Si) vs.heating rate of annealing were also discussed.
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