| FeSiB soft magnetic alloy occupies the mainstream position of amorphous alloy industry because of its high magnetic properties,low cost and good glass forming ability(GFA).The disordered structure of amorphous alloy not only makes it have higher resistivity,but also shows isotropy which makes it have lower coercivity.When a little of Cu and Nb elements are added to the formula of FeSiB amorphous alloy,a large number of nanocrystalline grains with similar size will be formed in amorphous matrix after proper heat treatment.When the amorphous matrix and nanocrystalline phase reaches a right proportion,the positive and negative magnetostrictive effects will cancel out,which will make the alloy have high permeability and very low coercivity.It will strengthen the strong exchange coupling between nanocrystalline grains,and make the alloy have higher saturation magnetization.Therefore,FeSiBNbCu nanocrystalline alloys have the advantages of easy magnetization,low coercivity,high permeability and high saturation magnetization,which greatly promote the application of amorphous-nanocrystalline alloys.The magnetic powder core prepared by FeSiBNbCu nanocrystalline alloy have excellent comprehensive soft magnetic properties.Because air gap and insulator can effectively increase resistivity,the nanocrystalline magnetic powder core hardly has skin effect,and has good frequency characteristics and low eddy current loss,which meets the requirements of electronic industry for lightweight,high frequency,miniaturization and low loss of inductors.Based on Fe73.5Si13.5B9Nb3Cu nanocrystalline alloy,the Fe80Si8B6Nb5Cu1 alloy was prepared by adjusting the proportion.Preparing powder by crushing the Fe80S18B6NbsCu nanocrystalline alloy,then powder was turned into magnetic powder core after coating,pressing and annealing.Through some characterization methods,the influence of different forming pressure and annealing temperature on the coercivity,permeability,loss and quality factor of magnetic powder core were studied and analyzed.Next,the soft magnetic properties of magnetic powder cores were investigated by adding hydrogen during annealing of Fe80Si8B6Nb5Cu alloy.Finally,adding different P content into(Fe80S18B6Nb5Cu)100-xPx alloy,then the effect of different P content on the soft magnetic properties of the core was studied.In this paper,the main four conclusions are as follows:(1)At lower forming pressure(500 Mpa-800 Mpa),the increasing of forming pressure will lead to the increase of internal stress and dislocation,which hinders the displacement of magenitc domain both increases coercivity and hysteresis loss;furthermore,the increasing of forming pressure will lead to the decrease of air gap,which increases the permeability;the more adequate insulator coating will increase resistivity and the decrease eddy current loss;however,the insulating layer is damaged and the internal stress is increase under excessive pressure.So the soft magnetic properties of the magnetic powder core will deteriorate sharply.Generally speaking,with the increase of forming pressure from 500 Mpa to 1000 Mpa,coercivity and permeability increase,loss and quality factor increase first and then decrease,and the most suitable forming pressure is 800 Mpa.(2)When annealing temperature is low(400 ?-490 ?),with the increase of annealing temperature,internal stress releases gradually,coercivity decreases,permeability increases gradually,unit mass loss decreases gradually,resulting in the increase of quality factor with the increase of annealing temperature;when annealing temperature is high(490 ?-550 ?),insulation layer is ablated,which makes the resistance of magnetic powder core larger.When the amplitude decreases,the amorphous phase becomes nanocrystalline,and the anisotropy of magnetocrystalline increases,the permeability,coercivity and hysteresis loss increase greatly,and the quality factor decreases.Overall,the effective permeability increases with the annealing temperature increasing from 400 ? to 550 ?.The coercivity and loss of the core decrease first and then increase,and the quality factor increases first and then decreases.The annealing temperature of Fe80Si8B6Nb5Cu nanocrystalline magnetic powder core is 490?.(3)In the process of hydrogenation,the oxygen content on the surface of powders decreases firstly and then tends to be stable.When the hydrogen content is low(0-1.2 mol),H atoms are filled into the gap of Fe atoms,which improves the amorphous forming ability of the alloys,and leads to the increase of resistivity,effective permeability and the decrease of coercivity,which gradually increases the saturated magnetic induction strength and quality factor of the magnetic powder cores.When the amount of hydrogen permeation is excessive(1.2 mol-2 mol),the effective permeability decreases,the coercivity increases,and the saturated magnetic induction and quality factor decreases.Considering the influence of hydrogen infiltration on the soft magnetic properties of magnetic powder cores,0.8 mol-1.2 mol H2 is the best choice during tempering of 1 kg Fe80SisB6NbsCu alloy,and the properties are improved remarkably.(4)With the increase of P content,the amorphous forming ability of the alloy first increases and decreases.When P content is less than 1 at.%,with the increase of P content,the amorphous forming ability of the alloy increases gradually,the coercivity and loss of the magnetic powder core also decrease gradually,and the resistivity and permeability increase slightly;when P content is 1 at.%to 2.5 at.%the amorphous forming ability of the alloy decreases rapidly with the increase of P content,resulting in the precipitation and growth of a large number of grains,the rapid increase of coercivity and loss,the increase of permeability first and then decrease,the rapid decline of resistivity and quality factor,and the sharp deterioration of the comprehensive properties of the magnetic powder core. |
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