Effects Of Composition And Processing Parameters On The Magnetic Properties Of Sm₂Fe₁₇N_x Permanent Magnet

The Sm2Fe17Nx compound has excellent intrinsic magnetic properties, whose anisotropy field is three times as large as that of Nd2Fe14B, and Curie temperature is 200K higher than that of Nd2Fe14B. This compound is a very promising candidate for permanent magnets. However, how to obtain Sm2Fe17 alloy consisting of a single phase was always troubling people since the discovery of Sm2Fe17Nx permanent magnets. At present, much attention was focused on inhibiting the formation of a -Fe phase and Sm-rich phase in the Sm-Fe parent alloy.In this thesis, we intended to eliminate the a -Fe phase by adjusting the composition and the cooling velocity. The effects of Sm content, cooling velocity and the additions of Nb and Zr on the microstructures of Sm-Fe alloys and magnetic properties of Sm2Fe17Nx were studied. Effects of nitrogenation techniques on magnetic properties were also studied.The a -Fe phase in parent Sm-Fe alloys can not be inhibited by increasing the Sm content. During nitrogenation process the Sm-rich phase decomposed into a -Fe phase and SmN phase, deteriorating the magnetic properties. Increasing the cooling velocity and additions of Nb and Zr can refine the a -Fe dendrites in as-cast alloys, decrease the amount of a -Fe phase after homogenization treatment. As a result, the magnetic.properties were improved.Long term ball-milling deteriorated the magnetic properties. The reason is the oxidation of the powder. When nitrogenation at 500 , the optimal nitrogenation time is 5 hours.