Research On Composition And Magnetic Properties Of Fe-Based Low Permeability Soft Magnetic Nanocrystalline Alloys

The Fe-based amorphous nanocrystalline material is a metallic soft magnetic material developed in the past 30 years.The Fe-based nanocrystalline material has the characteristics of high permeability,low loss and high saturation magnetic induction.Electronic devices such as filters,transformers,precision current transformers,high-frequency transformers,and common mode inductors used in some electric power fields,due to the presence of DC components in the working environment,rapidly saturate the device under the action of electromagnetic fields,resulting in a rapid decline in effective magnetic permeability.Therefore,the nanocrystalline alloys used in the above devices need to meet conditions such as lower initial magnetic permeability and the lowest possible coercive force to meet the requirements of power conversion or power measurement instruments.Fe-based nanocrystalline alloys have high magnetic permeability and poor linearity.In order to reduce the cost of strip production and meet the requirements of DC resistance,this study attempts to add a small amount of Ni to improve the DC resistance of Fe-based alloys.Ni has a negative magnetostrictive coefficient,and the addition of Ni can increase the magnetocrystalline anisotropy of the alloy,effectively reducing the magnetic permeability of the material,while also reducing the AC loss during the use of the material.The DC resistance of Fe-based nanocrystalline alloys with a small amount of Ni is significantly enhanced.Adding P element to replace Si element in the alloy can effectively reduce the magnetostrictive coefficient of the alloy and improve the magnetic permeability of the alloy,while P element can effectively refine the grain size and reduce the coercive force of the alloy.Therefore,it is attempted to use P element to replace Si element to further reduce the magnetic permeability and coercive force of the alloy.Finally,explore the impact of Mo on the amorphous formation ability,heat treatment stability,and soft magnetic properties of the alloy after replacement of Nb,and explore whether Mo can further improve the linearity of the alloy’s magnetic hysteresis loop and reduce the permeability of the alloy under this alloy system.Based on the VAC patent composition of FeNiSiBNbCu,this study investigates the effect of alloy composition on the nanocrystalline and amorphous forming ability,thermal stability,and soft magnetic properties of the alloy by replacing Fe with Ni,Si with P,and Nb with Mo.As the Ni content increases,the thermal stability of the alloy decreases,the onset temperature of primary crystallization gradually decreases,the onset temperature of secondary crystallization significantly decreases,and the temperature interval between the two crystallizations decreases.With the increase of Ni content,the hysteresis loop of the alloy gradually becomes flatter,the linearity increases,and the initial permeability decreases.Replacing Si with P can increase the temperature interval between crystallizations and improve the thermal processing range,which solves the problem of narrow crystallization temperature interval caused by excessive Ni content.At the same time,as the P content increases,the grain size gradually decreases,the anisotropy of the alloy decreases,and the coercivity decreases,while the initial permeability of the alloy gradually increases.A small amount of P replacing Si can reduce the solid solution Si content in the α-Fe(Si)phase of the alloy,thereby reducing the initial permeability of the alloy.After Mo replaces Nb,the FeNiSiBNbMoCu alloy can still maintain an amorphous state,but as the Mo content increases,the amorphous forming ability of the alloy gradually decreases.When Mo completely replaces Nb,a significant crystallization trend appears in the strip.With the increase of Mo content,the thermal stability of the alloy gradually decreases,and the increase of Mo content will cause the overlap of the two crystallization peaks,making the thermal processing conditions of the alloy more severe.After annealing,the alloy composition with higher Mo content has a larger grain size.The relative permeability of the alloy with higher Mo content decreases as the external field changes,and the direct current resistance of the alloy increases.However,with the increase of Mo content,the coercivity of the alloy will deteriorate sharply,which may lead to an increase in alloy loss.