IMPROVEMENT OF MAGNETIC-PROPERTIES OF MEC HANICALLY 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 n itriding. Sm2.5Fe17 and Sm2.3Fe17 alloy powders have been used as a st arting material. The oxygen content of the powders crystallized in vac uum is less than that of the powders crystallized in Ar atmosphere: it is less than 9000 ppm for the Sm2.5Fe17 powders. Consequently, the pr ecipitation of alpha-Fe, which deteriorates the rectangularity of thei r demagnetization curves, is suppressed. After MG for 72 ks and crysta llization in vacuum the nitrided Sm2.3Fe17 powders close to stoichiome tric Sm2Fe17, has also no alpha-Fe precipitation. The saturation magne tization and remanence are larger than those of the nitrided Sm2.5Fe17 powders.