Influence Of Interface Modification On The Magnetic Properties Of Nd₂Fe₁₄B/α-Fe Nanocomposite Magnets

The nanocomposite permanent magnets,which is composed of hard-magnetic phase and soft-magnetic phase in the nanometer scale range,have attracted much interest because of the much higher magnetic properties than the traditional permanent magnet.The interface plays an important role in the magnetic properties of nanocomposite permanent magnets.Therefore,it is of great significance to study the interface modification for the preparation of high performance nanocomposite permanent magnets.In this paper,Nd₂Fe₁₄B/α-Fe nanocomposite magnets ribbons and bulks were prepared by melt-spinning and hot pressing-thermal deformation methods.The microstructure of the Nd₂Fe₁₄B/α-Fe nanocomposite magnets was studied by employing X-ray diffraction（XRD）measurements and transmission electron microscope（TEM）observations,the magnetic properties of the magnets were studied by employing a vibrating sample magnetometer（VSM）.Nd₂Fe₁₄B/α-Fe nanocomposite permanent magnet ribbons were prepared by melt-spinning method.The interface was modified by adding Ti element and Nb element :the grain sizes of Nd2Fe14 B phase and α-Fe phase in NdFeTiNbB riboon were 23.1 nm and13.2 nm,which is smaller than that of NdFeB riboon,29.8 nm and 16.7 nm.The decrease of grain size increases the interfacial fraction in the single magnetic domain,and there is the interface amorphous phase in the NdFe TiNbB riboon The coercivity of the Nd₂Fe₁₄B/α-Fe nanocomposite permanent magnet ribbon after interface modification was increased from 5.9 kOe to 7.7 kOe without any decrease of remanence,moreover,the remanence ratio and the squareness of the loop were also improved obviously,the δM value was increased from 0.4 to 0.51,thus the maximum magnetic energy product increased from 21.8 MGOe to 23.4 MGOe.The Nd₂Fe₁₄B/α-Fe nanocomposite permanent magnet bulks were prepared by hot pressing and thermal deformation method.The interface was modified by adding low melting point Pr70Cu30 alloy and its effect on magnetic properties was studied.The coercivity,remanence and maximum magnetic energy product of the hot-pressing magnetswith Pr70Cu30 alloy added were increased synchronously with the annealing time extended.The（00l）crystallographic texture was produced in the hot deformed magnets added with Pr70Cu30 alloy,and the magnetic properties were greatly improved,the magnetic properties of the magnets obtained by the deformation after annealing When the strain changed in the range of 73% to 77%,the anisotropy of the magnets increased with the increase of strain,and the magnetic properties were improved.When the strain is 77%,the magnets were obtained the best magnetic properties.The magnetic properties were as follows: the remanence obtained by parallel to the magnetic field direction was 9.7 kG,the coercivity was 8.0 kOe,the maximum energy product was 19.9 MGOe.