Preparation And Property Investigation On Co-based Amorphous Soft Magnetic Alloys With Low Permeability

Cobalt-based amorphous alloys have been widely used in electronics and communication fields because of their high magnetic permeability,low coercivity,low loss,excellent wear resistance,good temperature stability and giant magneto-impedance effect,is the better materials for magnetic amplifier,common mode inductors,common mode choke and other electronic components.However,some special applications,such as with the DC superposition,or in the larger field magnetic field work,often require the material has a low permeability,because the permeability is too high to cause material saturation and failure potentially.Therefore,it is of great significance and practical value to explore cobalt-based amorphous alloys with low magnetic permeability and excellent soft magnetic properties.In this paper,CoFeSiBMn alloy system was selected as the research object,and the effect of Fe element addition and Si and B atomic ratio on the soft magnetic properties of CoFeSiBMn amorphous alloy was studied.Co_73-xFe_xSi₁4B₉Mn₄ and Co₇1Fe₂Si_14-xB_9+xMn₄ series amorphous alloys were prepared by single-roll quenching method.The difference with changing of Fe and Si/B ratio of magnetic properties such as saturation magnetic flux,coercivity,magnetic permeability and loss were studied.And the optimum atomic ratio was determined.On the basis of this,the effects of stress relief annealing and magnetic field heat treatment on the soft magnetic properties were investigated,and the optimum heat treatment parameters were established.The results show that in the Co_73-xFe_xSi₁4B₉Mn₄ alloy system,the saturation magnetic induction of Co_73-xFe_xSi₁4B₉Mn₄ amorphous alloy increases gradually with the increase of Fe content,and the coercivity decreases first and then increases,then the effective permeability is opposite to that of coercivity.The appropriate amount of Fe can effectively reduce the loss of quencher Co_73-xFe_xSi₁4B₉Mn₄ amorphous alloy and improve the high frequency performance of the alloy.Co₇1Fe₂Si₁4B₉Mn₄ amorphous alloy has the best comprehensive soft magnetic properties,the saturation magnetic induction intensity is 0.88 T,the coercivity is 1.29 A/m,the effective permeability is 5360,under the conditions of 0.2T/20kHz and 0.5T/20kHz,the loss are 36.8 W/kg,126.8 W kg,respectively.Changing the relative content of Si and B elements,and to study the effect of Si and B atomic ratio on the thermal and soft magnetic properties of quencher Co₇1Fe₂Si_14-xB_9+xMn₄ amorphous alloy.It is found that the Curie temperature of Co₇1Fe₂Si_14-xB_9+xMn₄ amorphous alloy increased obviously with the decrease of Si content,and the initial crystallization temperature increased first and then decreased,and the thermal stability of the alloy is increased.The saturation magnetic induction intensity of the quenched Co₇1Fe₂Si_14-xB_9+xMn₄ amorphous alloy increases with the increase of the content of B,and the coercivity decreases and then increases.The effective permeability increases with the coercivity in contrast.When the atomic ratio of Si and B is close to 1:1,the loss of Co₇1Fe₂Si_14-xB_9+xMn₄ amorphous alloy is the highest,and with the further increase of B content,the loss of Co₇1Fe₂Si_14-xB_9+xMn₄ amorphous alloy decreases,high frequency performance becomes good.Co₇1Fe₂Si₉B₁4Mn₄ amorphous alloy has the best comprehensive soft magnetic properties,including saturated magnetic induction strength of 0.96 T,coercivity of 1.21 A/m,effective permeability of 5510,under the conditions of 0.2T/20kHz and 0.5T/20kHz,the loss are 34.8 W/kg and 119.9 W/kg respectively.The effect of stress relief annealing on the coercivity and permeability of the alloy was studied.The optimum annealing temperature is 415 ℃ and the holding time is 5 min.On the basis of this,the effect of transverse magnetic field heat treatment on the soft magnetic properties of Co₇1Fe₂Si₉B₁4Mn₄ amorphous alloy was studied.The results show that the transverse magnetic field heat treatment can make the hysteresis loop of the alloy flat,effectively reduce the permeability,and the permeability in the 1k-1MHz wide frequency range tends to be constant.The optimum heat treatment temperature is set to 240 ℃,the magnetizing current is 150 A,and the holding time is 90 min.The soft magnetic properties of CoFeSiBMn series amorphous alloy,with changing of Fe,Si and B contents,under the condition of the best magnetic field heat treatment process were studied.The Co₇1Fe₂Si₉B₁4Mn₄ amorphous alloy has the best properties with low magnetic permeability and coercivity,are 2960,and 2.29 A/m,respectively.Sometime,when the DC field of 325A/m was superimposed,the alloy sample can still maintain 91%of the permeability.In this paper,the effect of transverse magnetic field heat treatment on the soft magnetic properties of CoFeSiBMn series amorphous alloy was studied in order to solve the problem that the soft magnetic material was easy to saturate during the practical application,which procides reference for exploring the preparation process of soft magnetic material with low permeability.The CoFeSiBMn series with low permeability amorphous alloys have application prospects in the field of electronic devices.such as switching power transformers and high performance pulsed magnetic switches.