Abstract
Changes in the coercive force (Hc) of gas-atomized Nd-Fe-B powder were measured as functions of annealing temperature and particle size. The Hc of the powder (sieved to a particle size of <44 μm) increased with increasing annealing temperature, reached a maximum at 600°C and then decreased. In the Hc particle size dependence curves, the maximum levels of Hc of as atomized and annealed powders at 600°C were observed in the 60-90 μm and 10-20μm diameter size ranges, respectively. The 10-20 μm diameter powder annealed at 600°C for two hours exhibited an Hc of more than 10 KOe. The experimental results indicated that the Hc of Nd-Fe-B gas-atomized powder was dependent on strain and grain size as well as on the structure of the matrix phase and grain boundary.
