Artigo de peri??dico
d-HDDR processing of Nd-Fe-B based alloys to obtain highly anisotropic nanocrystalline powders
Registro en:
1662-9752
899
10.4028/www.scientific.net/MSF.899.563
Autor
ENGERROFF, JULIANO A.B.
KELLER, FREDERICO O.
LOPES, LEONARDO U.
MASCHERONI, ARTHUR A.
TAKIISHI, HIDETOSHI
WENDHAUSEN, PAULO A.P.
Resumen
The HDDR (hydrogenation-disproportionation-desorption-recombination) process is an
established powder metallurgy route to obtain Nd???Fe???B nanocrystalline powders for bonded
magnets manufacturing. Therefore, both conventional (c-HDDR) and dynamic HDDR (d-HDDR)
processes has been investigated to obtain Nd-Fe-B-based powders with different characteristics.
Magnetic properties were measured by means of a hysteresisgraph and the powder obtained by d-
HDDR showed strong anisotropy, allowing a Br of 1.1 T in the bonded magnet, whereas c-HDDR
powder was isotropic with a Br of 0.6 T. Microstructural changes were characterized by X-ray
diffraction (DRX) and scanning electron microscopy (SEM). X-ray patters of anisotropic powders
made by d-HDDR showed high intensity reflection peaks indexed as (004), (105) and (006) planes
in the aligning direction, due the texture inducement in c-axis of the main phase (Nd2Fe14B).
However, SEM micrographs of c-HDDR powder showed a more homogeneous microstructure, with
grain size of ~300 nm, when compared to d-HDDR powder that ranged from 300 nm to 500 nm.
This difference is assumed to be the cause of lower intrinsic coercivity found in the c-HDDR
powder.