Abstract
Precipitated crystal grain size in sintered Nd15Fe7711B8 and Nd15Fe76Al111B8 permanent magnets with different heat treatments has been examined by a very small-angle neutron scattering experiment using channel-cut perfect crystals. The results indicate that the chemical microstructures observed are in the range of about 4–6µm, and those in Nd15Fe76Al111B8 are larger than in Nd15Fe7711B8. This simply suggests that the Al-substitution affects the sintering mechanism and results in the increase of the size of precipitates and high coercive force.