The influence of process parameters and alloy structure on the magnetic properties of NdDyFeBNb HD sintered magnets

Sintered permanent magnets based on the compositions Nd14.5Dy1.5Fe76B7Nb1 and Nd16Fe76B8 have been produced using the hydrogen decrepitation (HD) process. The effects of process parameters upon the magnetic properties of Nd-based magnets have been studied. It is shown that grain growth occurs in the sintered magnets produced from very fine powders. This work also shows that the influence of the alloy microstructure on the magnetic properties of Nd–Dy–Fe–B–Nb sintered permanent magnets is significant. Magnets produced from the fine grained alloy (near equiaxed grains) exhibited superior intrinsic coercivities to those produced from the as-cast ingot (large columnarlike grains).