Preparation And Soft Magnetic Properties Of FeCo-based Amorphous Nanocrystals

Fe-based amorphous nanocrystals,as one of soft magnetic materials,have excellent soft magnetic properties,mechanical properties and low preparation cost.Therefore,they are widely used in the fields of new energy,5G communications.In order to further improve the soft magnetic properties of Fe-based amorphous nanocrystalline alloy and make it more widely used.it is necessary to improve B_s but reduce H_c.Generally,the increasement of ferromagnetic elements contents(such as Fe,Co,etc.)in the alloy is the most simple and effective way to improve B_s.However,when the content of ferromagnetic elements in the alloy increases,the contents of nonmagnetic elements(such as P,Si,Cu,etc.)that improve the ability of amorphous formation will inevitablely decline,then the soft magnetic properties of the alloy will be affected.Therefore,it is of great significance to develop an FeCo-based amorphous nanocrystalline alloy with a high B_s,low H_c and high amorphous forming ability.In this paper,two types of FeCo-based amorphous/nanocrystalline soft magnetic system,namely(Fe_0.8Co_0.2)_98-xB_xSi₁Cu₁(x=13,14,15,16)and(Fe_0.8Co_0.2)_98-xB_xSi₁P₁(x=13,14,15,16),were prepared through the process of rapid quenching.Subsequently,the amorphous forming ability,thermal stability and soft magnetic properties of the two alloy systems were studied by the substitution of Cu and P elements,changing the element ratio,optimizing the composition of the soft magnetic alloy,and using different heat treatment processes to heat the ribbons.Besides,XRD,TEM,SEM,DSC,SQUID and so on were employed to characterize the microstructure,surface morphology,thermal stability,amorphous forming ability and soft magnetic properties of the FeCo-based amorphous nanocrystalline alloys.The results of the paper are as follows:(1)In the(Fe_0.8Co_0.2)_98-xB_xSi₁Cu₁(x=13,14,15,16)series alloys,the ribbons are crystalline when the content of B is 13 at.%.As the B content increases,the ribbons present an amorphous state,which indicates that the amorphous forming ability of the alloy system increases significantly.And the initial crystallization temperature and the reduced glass transition temperature all gradually increase with the increase of B content,indicating that the thermal stability of the ribbons and the amorphous formation capacity increase with the increase of the B content.(2)The effect of different heat treatment processes on the soft magnetic properties and microstructure of the(Fe_0.8Co_0.2)_98-xB_xSi₁Cu₁(x=13,14,15,16)series alloys.The results show that a large number of spherical symmetric clusters and translational symmetric clusters appeared in the amorphous ribbon at appropriate heat treatment temperature and maintaining time(3 min),which caused the microstructures of the ribbons transform from a disordered state to an ordered state.At this time,the saturation flux density of the alloy reached the maximum value 1.80 T.However,when the heat treatment time is increased to 10 min,the alloy is over-annealed,and the grain size is too large.And the saturation flux density reduces due to the interaction of exchange coupling effect decreases.(3)(Fe_0.8Co_0.2)_98-xB_xSi₁P₁(x=13,14,15,16)ribbons all show amorphous state and display obvious glass transition temperature.Moreover,the initial crystallization temperature of(Fe_0.8Co_0.2)_98-xB_xSi₁P₁(x=13,14,15,16)ribbons are significantly higher than these(Fe_0.8Co_0.2)_98-xB_xSi₁Cu₁(x=13,14,15,16)ribbons.Therefore,it can be inferred that the amorphous forming ability and thermal stability of the Fe-Co-B-Si system improve more for P element addition than that of Cu element addition.