MAGNETIC-PROPERTIES OF SINTERED PERMANENT-MAGNETS - PR-FE-CU-B, ND-FE-CU-B

Radially anisotropic Pr15Fe77.5Cu1.5B6 permanent magnets nave been prepared from hydrogen decrepitated (HD) powders by conventional powder metallurgy processes. The best magnetic properties obtained along the radial directions are as follows: (BH)max = 10.5 MGOe, Br = 7.5 kG, and iHc = 8.5 kOe. Since Pr2(Fe, Cu)14BHx exhibits planar anisotropy, the tetragonal c-axis of the HD powders should lie in the plane perpendicular to the field direction during alignment compaction. This style of radial alignment is not changed in the subsequent dehydrogenation and sintering processes. The easy direction of magnetization of the magnet can be changed by alloy design, switching from radial directions to the field direction with the addition of 33 wt% or more of Nd-Fe-B. Further addition of Nd-Fe-B monotonically increases both Br and (BH)max. For the Nd-Fe-Cu-B system, a small concentration of 1.5 at% Cu dramatically deteriorates the magnetic properties of the sintered magnet due to the extensive precipitation of free iron. © 1990 IEEE