NANOSTRUCTURE OF MECHANICALLY ALLOYED ZINC-BONDED SM2FE17NX MAGNETS

The nanostructure of mechanically alloyed Sm2Fe17Nx-based magnets, whi ch were Zn-bonded by pressure-assisted sintering at elevated temperatu re, was characterized by means of high-resolution and analytical trans mission electron microscopy. The hard magnetic Sm2Fe17Nx grains were f ound to be about 100 nm in average size separated by a nonmagnetic Zn- rich phase of 5-10 nm in thickness. High-resolution imaging revealed v arious lattice planes in the grain boundary region which may be attrib uted to the presence of Gamma-Fe-Zn. Obviously, this nonmagnetic phase at the grain boundaries provides additionally magnetic decoupling of the individual Sm2Fe17Nx grains, which is responsible for the coercivi ty increase of up to 50% induced by the pressure-assisted Zn bonding p rocess.