Recombination characteristics of the Nd-Fe(-Co)-B(-Ga-Zr)-type anisotropichydrogenation, desorption, disproportionation, recombination alloys

The recombination characteristics of the Nd-Fe-B-type isotropic and anisotr opic hydrogenation, desorption, disproportionation, recombination (HDDR) al loys were investigated using three types of alloys: alloy A (Nd12.6Fe81.4B6 ), alloy B (Nd12.6Fe81.3B6Zr0.1), and alloy C (Nd12.6Fe68.8Co11.5B6Ga1.0Zr0 .1). Alloy A is featured with the isotropic HDDR character, while alloys B and C are featured with the anisotropic HDDR character. Recombination chara cteristics of the alloys were examined by observing the coercivity variatio n as a function of recombination time. Microstructural development during t he HDDR was examined by means of transmission electron microscopy, and it w as correlated with the coercivity variation. The present study revealed tha t the intrinsic coercivities of the recombined materials rapidly increased with increasing the recombination time and then showed a peak, after which the coercivities decreased gradually as usual. However, it has been found t hat the degraded coercivity was recovered significantly on prolonged recomb ination. Compared with the isotropic HDDR alloy A, the anisotropic HDDR all oys B and C are notable for their greater recovery of coercivity. The signi ficant recovery of coercivity was accounted for in terms of the development of a well-defined smooth grain boundary between the recombined grains on p rolonged recombination. (C) 1999 American Institute of Physics. [S0021-8979 (99)57208-3].