ISSN:
1089-7550
Source:
AIP Digital Archive
Topics:
Physics
Notes:
Anisotropic Nd–Fe–B magnet powders can be produced by the hydrogenationdecomposition-desorption-recombination (HDDR) process from Nd–Fe–B–Co–M (M=Ga, Zr, Nb, Hf, and Ta) alloys. The present status of those HDDR powders and the bonded magnets made from them are reviewed with regards to the powder particle size dependence of their magnetic properties, their magnetic thermal stability, and their magnetization behavior. The results of a mechanistic study on the recombination step are also presented. The magnetic properties of the anisotropic HDDR powder depend relatively little on the powder particle size. Bonded magnets with a density of ∼6.20 g/cm3 and a BHmax of 18.5–20.5 MGOe can be produced from anisotropic HDDR powders with particle sizes of below 300 μm diam. The temperature coefficient of the intrinsic coercive force iHc, of the bonded magnet is −0.55%/°C in the temperature range from 25 to 100 °C. The magnetization force needed for full magnetization of the bonded magnet is about twice the coercive force of the magnet, indicating that the magnetization mechanism is different from that of the rapidly solidified isotropic Nd–Fe–B magnet. In the early stage of the recombination step of the HDDR process (1 min desorption), three phases are produced, i.e., α-(Fe,Co), spherical NdH2 and rimlike Nd2(Fe,Co)14B surrounding the NdH2 particle. Further desorption makes the Nd2(Fe,Co)14B phase grow. © 1996 American Institute of Physics.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1063/1.361567
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