Improvement of magnetic properties of mechanically grinding ground Sm2Fe17Nx powders by vacuum heat treatment

Sm2Fe17Nx permanent magnetic powders have been prepared by mechanical grinding (MG) and subsequent heat treatments for crystallization and nitriding. Sm2.5Fe17 and Sm2.3Fe17 alloy powders have been used as a starting material. The oxygen content of the powders crystallized in vacuum is less than that of the powders crystallized in Ar atmosphere: it is less than 9000 ppm for the Sm2.5Fe17 powders. Consequently, the precipitation of alpha-Fe, which deteriorates the rectangularity of their demagnetization curves, is suppressed. After MG for 72 ks and crystallization in vacuum the nitrided Sm2.3Fe17 powders close to stoichiometric Sm2Fe17, has also no alpha-Fe precipitation. The saturation magnetization and remanence are larger than those of the nitrided Sm2.5Fe17 powders.