Investigation of Morphologic Analyses on Fracture of RE2TM17 Type Permanent Magnet

Three kinds of sintered Sm2TM17 magnets with difference properties are studied. The content of oxygen in three samples is analyzed. The microstructure observations by SEM are taken on the fractures surface, which differ from the polished and etched surface we usually use. The SEM morphologic pictures are presented for the fractures of magnets. It is found that many fine grains, whose size is 1–2 μm, are precipitated on the pore wall (the pore size typically is about 10 μm). The chemical compositions analyzed by micro-probe indicate that the fine grains are oxide with main content Sm2O3. It illustrates that the formation of the large pores can be attributed to the oxidation of the samarium. The experiment results in SEM and oxygen content for the 2:17 magnet samples reveal that the higher the oxygen content, the more pores and the poorer the property.