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| Study on the HDDR Characteristics of the Nd-Fe(-Co)-B(-Ga-Zr)-type Alloys |
| Journal of Magnetics, Volume 4, Number 4, 31 Dec 1999, Pages 131-135 |
| S. W. Shon(Pukyong National University), H. W. Kwon(Pukyong National University), D. I. Kang(Pukyong National University), Yoon. B. Kim(Korea Institute of Science and Technology), W. Y. Jeung(Korea Institute of Science and Technology) |
| Abstract |
| The HDDR characteristics of the Nd-Fe-B-type isotropic and anisotropic HDDR alloys 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). The alloy A is featured with the isotropic HDDR character, while alloy B and C are featured with the anisotropic HDDR character. Hydrogenation and disproportionation characteristics of the alloys were examined using DTA under hydrogen gas. Recombination characteristics of the alloys were examined by observing the coercivity variation as a function of recombination time. The present study revealed that the alloy C exhibits slightly higher hydrogenation and disproportionation temperatures compared to the alloy A and B. Recombination of the anisotropic alloy B and C takes place more rapidly with respect to the isotropic alloy A. 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. The degraded coercivity was, however, recovered significantly on prolonged recombination treatment. Compared with the isotropic HDDR alloy A the anisotropic HDDR alloy B and C are notable for their greater recovery of coercivity. The significant recovery of coercivity was accounted for the in terms of the development of well-defined smooth grain boundary between the recombined grains on prolonged recombination. |
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