Influence Of Magnetic Field Annealing On The Soft Magnetic Properties For FeCo-based Nanocrystalline Alloys

We studied the effect of Al addition and magnetic field annealing on the structure and soft magnetic properties of(Fe_0.5Co_0.5)_73.5Si_13.5Nb₃Cu₁B_9-xAl_x?x=0,1,2,3?and(Fe_0.5Co_0.5)_73.5Si_13.5Nb₃Cu₁B_9-xAl_x?x=0.2,0.4,0.6,0.8?alloys.The variations of <K>and ?s for the dual-phase nanocrystalline alloys were mainly discussed.We use impedance analyzer to measure the variation of initial permeability ?i with temperature T??i-T curves?for the annealed alloys to study the high-temperature permeability.XRD showed that the dual-phase nanocrystalline structure was formed in the studied alloys after vacuum annealing.We use differential scanning calorimetry?DSC?to determine the crystallization temperature of amorphous ribbons.According to the ?i^T curves for as-quenched alloys,the Curie temperature of amorphous alloys were detected,which offered the basis of magnetic field annealing temperature.The experimental results showed that in the(Fe_0.5Co_0.5)_73.5Si_13.5Nb₃Cu₁B_9-xAl_x?x=0,1,2,3?alloys,replacing B with Al can reduce the first crystallization temperature Tx1 and increase the second crystallization temperature Tx2,therefore?Tx?Tx2-Tx1?was enlarged from 206? to 256? with Al content increasing from 0 to3.The ?i-T curve showed that with the increase of Al content,the soft magnetic properties first increased and then decreased,the 530? annealed(Fe_0.5Co_0.5)_73.5Si_13.5Nb₃Cu1B8Al1 alloy had the minimum average grain size,it performed the best high-temperature soft magnetic properties.After magnetic field annealing,the ?s reduced and <K> increased.It can be seen that low temperature magnetic field annealing mainly affect the room temperature initial permeability,high temperature magnetic field annealing can change the high-temperature magnetic property significantly.The 530? magnetic field annealed(Fe_0.5Co_0.5)_73.5Si_13.5Nb₃Cu1 B8Al1 alloy showed excellent high temperature soft magnetic properties and the initial permeability can also remain above 1500 at 650?,the discovery has very important practical significance to the application of FeCo-based nanocrystalline alloys.The ? T of(Fe_0.5Co_0.5)73.5 Si13.5Nb3 Cu1B9-x Al_x?x=0.2,0.4,0.6,0.8?alloys was not changed obviously compared with the high Al alloys,The ?i-T curve of 550? annealed samples was no significant difference between each other,and the initial permeability values were greatly reduced compared with high Al alloys,this may be due to the effect of lower Al on FeCo-based alloys is small.When the annealing temperature wasabout 600?,minimum grain size was 12.5nm for the x = 0.6 sample,which made the x = 0.6 sample obtain the best soft magnetic property.