| Rare earth permanent magnet have excellent magnetic property from NdFeB to SmCo, not only TbCu7-type SmFeN permanent magnetic materials have excellent magnetic property, but high heat-resisting and corrosion resistant performance. It can be prepared into a complex magnet because of the isotropic characteristic, low content of Sm, low cost and which is a promising new type bonded rare earth permanent magnet materials. High melting point of SmFe alloy damage to rapid quenching equipment, however, alloy melting point can be lower, the Curie temperature can be improved. At the same time, there is no change upon the phase structure. On the other hand, rapid quenching wheel speed can be lower and refine the grain through adding a low melting point elements., which can improve the magnetic.In this paper, Sm(Fe, M)9(M=Ga, Nb) alloy are prepared by melt-spun method, through X-ray diffraction(XRD), vibrating vample magnetometer(VSM), differential scanning calorimetry(DSC), scanning electron microscopy(SEM), high-resolution transmission electron microscopy(HRTEM), et al. The influence of the Sm content on the phase structure was systematic researched, eventually confirming the content of Sm. At the same time, the phase structure, microstructure, Curie temperature, alloy melting point, magnetic properties and coercivity mechanism was systematic studied through adding Ga and Nb elements, and on the basis of the theory of crystallization, crystallization kinetics of the SmFe alloy bonded Ga and Nb was investigated, analyzing the magnetic properties. Through the research, conclusion was been made as follows:(1) The composition SmyFe10-x-yGax are prepared by melt-spun method at wheel speed of50m/s, the influence of the Sm content on the phase structure was systematic researched, eventually a single TbCu7type structure was generated when y=0.98. Fe-Fe dumbbell inter-distance was augmented because Ga atom have partialiy occupies Fe2e,3g,61sites, and the average magnetic moment Fe (μFe) atoms was increased, therefore, An obvious development of the Curie temperature is obtained with the increased Ga content from x=0～1(△Tc=90℃). Adding Ga element fine grains, there is the smallest grain size27nm when x=0.25, at the same time, an obvious decline (△Tm=50℃) of alloy melting point is obtained with the increased Ga (x=0-1), positron annihilation experiments show that the SmFe alloy vacancy concentration was decreased through doping Ga element, the defects in alloy was reduced, phase structure yield a tendency of2:17type.(2) After heat treatment at800℃, positron annihilation test indicated that a single vacancy defects had combined into vacancy clusters in rapid quenching ribbons, as a result, positron annihilation rate and effective nitriding position increase, eventually magnetism will increase, it is necessary to crystallize treatment SmFeGa alloy. There is a optimum magnetic propertiy Hcj=7.90kOe, Br=6.3kGs,(BH)max=5.54MGOe after crystallization treatment at750℃-900℃(interval of50℃) for60min and nitride treatment at460℃for12h when x=0.25. It can be seen that SmFeGa nitrides were composed of hard and soft magnetic phase from XRD, soft magnetic phase grain size greater than30nm from Rietveld refinements, henkel curve shows grain size too greater to generate exchange coupling effect, meanwhile demagnetization curve exist a obvious "step", which deteriorated magnetic properties energy. The coercivity of SmFeGa nitrides is first increase then decrease with the increase of the content of Ga. At the magnetic field, SmFeGa nitrides was suffered from pinning effect when x=0.25, which is derived from the grain boundary of hard magnetic phase or magnetic domain-wall. The smaller the grain size, the higher coercivity.(3) Melt spinning SmFeGa alloy promote SmFeg phase formation, restrain the α-Fe due to a high melting point elements Nb doping. The composition Sm0.98(Fe0.95Co0.05)8.77-x Ga0.25Nbx are prepared by melt-spun method at different wheel speed, alloy structure were composed of SmFeg and segmental amorphous phase when x>0.3, Vs>50m/s, while the smaller the Nb content, the lower the wheel speed, alloy structure were composed of2:17-type structure and α-(Fe, Co) phases. There is a optimum magnetic propertiy Hcj=10.1kOe, Br=7.6kGs,(BH)max=9.3MGOe after crystallization and nitriding treatment when x=0.2, magnetic energy product has been improved4MGOe compared to the best magnetic properties of SmyFe10-x-yGax nitrides. It is can been seen that the demagnetization curve "step" become smaller, which indicates that deterioration of magnetic performance decrease, and soft magnetic phase soft magnetic phase grain size is less than30nm from TEM, uniformly, henkel plots indicate that there is still no exchange coupling. With the increase of the content of Nb, coercivity mechanism have changed from pinning (x=0,0.1,0.2) to nucleation (x=0.3), while there is exsiting pinning effect for nucleation control in low magnetic field. The more the Nb content, the greater crystallization activation energy by calculating Kissinger curve, which show that the stability of the amorphous phase is greater, it is necessary for crystallization to need higher energy over-the-Barrier. Amorphous phase was promoted for SmFeGa alloy bonded by Nb, refining grain size increase effective position of nitriding, consequently, SmFeN magnetic properties can drastic be improved. |
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