Preparation And Soft Magnetic Properties Of Fe_84.3Si₄B₈P_3-xCu_0.7M_x（M=C,Nb）Amorphous Nanocrystalline Alloys

As a new green energy-saving soft magnetic material,the research and application of Fe-based amorphous nanocrystalline alloys have attracted more and more attention.Compared with traditional soft magnetic materials,Fe-based amorphous nanocrystalline alloys have the advantages of excellent soft magnetic properties,simple production and less energy consumption in the process of production and use,and have been widely used in the field of distribution systems such as motors and transformers.The Fe content of Fe-based amorphous nanocrystalline materials are generally low in the actual production,resulting in low saturation magnetic flux density of the alloys.However,for nanocrystalline alloys with high saturation magnetic flux density,the amorphous forming ability of the alloys are low because of the high Fe content,which is difficult to obtain amorphous phase in the as-spun ribbon in the actual production process.Therefore,solving the problem of amorphous forming ability and improving the soft magnetic properties of Fe-based alloys have become the research focus of nanocrystalline alloys.In this thesis the Fe_84.3Si₄B₈P₃Cu_0.7alloy was used as the basic composition,and the element substitution method is used to further optimize the composition.According to the analysis of elemental properties,the P element in the alloy was replaced by C and Nb elements,respectively,and the ribbon was prepared by single copper roller melt spinning method.The effect of the substitution of elements on the amorphous forming ability and thermal stability of the alloys under quenching were studied.At the same time,the amorphous alloy ribbon was annealed by rapid annealing method to prepare nanocrystalline alloys,and the soft magnetic properties,phase structure and microstructure of the annealed alloy ribbon were studied.When the melt spinning speed is 48 m/s,the crystallization peaks of Fe_84.3Si₄B₈P_3-xCu_0.7C_x（x=0,1,2,3）alloy ribbons prepared by replacing P element in Fe_84.3Si₄B₈P₃Cu_0.7alloy disappear gradually with the increase of C content.When x=2 and 3,The diffraction peaks of crystalline phase disappear and only the diffuse scattering peak is observed,indicating that the prepared alloy forms a completely amorphous structure.The differenceΔT_xbetween the first crystallization temperature T_x1and the second crystallization temperature T_x2increases with the increase of C content.When x=2,ΔT_xreaches a maximum of 165°C.The as-spun amorphou_Is_I ribbon was annealed at T_x1afor 150 s,the saturation magnetic flux intensity（B_s）of amorphous alloy ribbon reaches a maximum of1.88 T at x=3.The coercivity（H_c）reaches a minimum value of 3.7 A/m at x=2.The Fe_84.3Si₄B₈P_3-xCu_0.7Nb_x（x=0,1,2,3）alloy ribbons were prepared by substituting Nb element for P element in Fe_84.3Si₄B₈P₃Cu_0.7alloy at the melt spinning speed of 48 m/s,and only the alloy with x=3 are completely amorphous.The Fe_84.3Si₄B₈P_3-xCu_0.7Nb_x（x=0,1,2,3）alloy ribbons are completely amorphous with the melt spinning speed increasing to 51m/s.When x=3,the maximum annealing temperature windowΔT_xis 199°C.After 150 s annealing at T_x1,the B_sreaches the maximum of 1.82 T in the Nb free alloy and decreases with the increase of Nb content.The coercivity（H_c）decreases with the increase of Nb element and reaches the minimum value of 2.2 A/m when x=3.