ANISOTROPIC HDDR EPOXY BONDED MAGNETS FROM NDFEBZR

The Hydrogenation Disproportionation Desorption Recombination (HDDR) process has been established as an effective processing route for the production or isotropic NdFeB coercive powder. By the addition of very small amounts of zirconium to the initial composition, it has also been found that anisotropic powder can be produced during the HDDR process. Two compositions were selected for this work; Nd16Fe75.9B8Zr0.1 and Nd16Fe75.7B8Zr0.3. These alloys were processed at temperatures between 770-degrees-C - 840-degrees-C and it was found that a maximum coercivity of 800 kA/m was achieved for the alloy containing 0.1 at.% Zr at a processing temperature of 795-degrees-C, but the alloy containing 0.3 at.% Zr failed to exhibit any coercivity greater than 120 kA/m, across a wide range or processing temperatures. This can be attributed to a much larger final grain size for this material under the processing conditions employed in this work. Magnetic anisotropy is produced by the submicron grains of Nd2Fe14B recombining from the disproportionated structure with a preferred orientation distribution. The mechanism for this process has not yet been established.