Hostname: page-component-8448b6f56d-t5pn6 Total loading time: 0 Render date: 2024-04-18T00:43:28.452Z Has data issue: false hasContentIssue false
  • English
  • Français

Desorption–recombination and microstructure change of a disproportionated nanostructured NdFeB alloy

Published online by Cambridge University Press:  31 January 2011

Hu Lianxi ,
Li Yuping ,
Yuan Yuan  and
Shi Gang
Hu Lianxi*
Affiliation:
School of Material Science and Engineering, Harbin Institute of Technology, Harbin 150001, People’s Republic of China
Li Yuping
Affiliation:
School of Material Science and Engineering, Harbin Institute of Technology, Harbin 150001, People’s Republic of China
Yuan Yuan
Affiliation:
School of Material Science and Engineering, Harbin Institute of Technology, Harbin 150001, People’s Republic of China
Shi Gang
Affiliation:
School of Material Science and Engineering, Harbin Institute of Technology, Harbin 150001, People’s Republic of China
*
a) Address all correspondence to this author. e-mail: hulx@hit.edu.cn
Get access

Abstract

The desorption–recombination behavior of a mechanically disproportionated, nanostructured Nd12Fe82B6 alloy was investigated by differential scanning calorimetry and thermogravimetric analysis. The microstructure change due to desorption–recombination treatments at various temperatures was characterized by x-ray diffraction, Mössbauer study, and transmission electron microscopy observation. The results show that the hydrogen desorption of the as-disproportionated alloy occurs in two stages: (i) the partial dehydriding of the Nd hydride from Nd2H5 to NdH2, as well as the desorption of the hydrogen absorbed/adsorbed at sites of crystal defects but not in the form of Nd hydride, at temperatures between 180 and 460 °C; and (ii) the complete dehydriding of the Nd hydride from NdH2 to Nd at temperatures between 630 and 780 °C. The recombination of α-Fe with Fe2B and Nd to form Nd2Fe14B occurs following the dehydriding of NdH2 to Nd, and it acts as the controlling step for the whole desorption–recombination process. The kinetics of both the desorption–recombination reaction and the growth of the newly formed Nd2Fe14B grains accelerate with increasing temperature. For a fixed annealing time of 30 min, the optimal processing temperature seems to be 760 °C, which gives rise to a fully recombined Nd2Fe14B–α-Fe nanocomposite microstructure with Nd2Fe14B and α-Fe phases of 25–30 nm in average size.

Keywords

MicrostructureNanostructureNd
Type
Articles
Information
Journal of Materials Research , Volume 23 , Issue 2 , February 2008 , pp. 427 - 434
Copyright
Copyright © Materials Research Society 2007

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

REFERENCES

1Skomski, R.Coey, J.M.D.: Giant energy product in nanostructured two phase magnets. Phys. Rev. B: Condens. Matter 48, 15812 1993CrossRefGoogle ScholarPubMed
2Coey, J.M.D.: Magnetic materials. J. Alloys Compd. 326, 2 2001CrossRefGoogle Scholar
3Manaf, A., Buckley, R.A.Davis, H.A.: New nanocrystalline high-remanence Nd–Fe–B alloys by rapid solidification. J. Magn. Magn. Mater. 128, 302 1993CrossRefGoogle Scholar
4Kramer, M.J., Lewis, L.H., Fabietti, L.M., Tang, Y., Miller, W., Dennis, K.W.McCallum, R.W.: Solidification, microstructure refinement and magnetism in Nd2Fe14B. J. Magn. Magn. Mater. 241, 144 2002CrossRefGoogle Scholar
5Miao, W.F., Ding, J., McCormick, P.G.Street, R.: Structure and magnetic properties of mechanically milled Nd2xFe100−3xBx (x = 2-6). J. Alloys Compd. 240, 200 1996CrossRefGoogle Scholar
6Neu, V., Crespo, P., Schafer, R., Eckert, J.Schultz, L.: High remanence Nd–Fe–B–X (X = Cu, Si, Nb3Cu, Zr) powders by mechanical alloying. J. Magn. Magn. Mater. 157–158, 61 1996CrossRefGoogle Scholar
7Chen, Z.M., Zhang, Y., Ding, Y.Q., Hadjipanayis, G.C., Chen, Q.Ma, B.M.: Studies on magnetic properties and microstructure of melt-spun nanocomposite R 8(Fe,Co,Nb)86B6 (R = Nd, Pr) magnets. J. Magn. Magn. Mater. 195, 420 1999CrossRefGoogle Scholar
8Bauer, J., Seeger, M.Kronmuller, H.: Magnetic properties and microstructural analysis of rapidly quenched FeNdBGaNb permanent magnets. J. Magn. Magn. Mater. 139, 323 1995CrossRefGoogle Scholar
9Takeshita, T.Nakayama, R.: Magnetic properties and microstructures of Nd–Fe–B magnet produced by hydrogen treatment in Proceedings of the 10th International Workshop on Rare Earth Magnets & Their Applications Kyoto,,1989 1, 551Google Scholar
10McGuiness, P.J., Zhang, X.J., Yin, X.J.Harris, I.R.: Hydrogenation, disproportionation and desorption (HDD): An effective processing route for Nd–Fe–B-type magnets. J. Less-Common Met. 158, 359 1990CrossRefGoogle Scholar
11Harris, I.R.McGuiness, P.J.: Hydrogen: Its use in the processing of NdFeB-type magnets. J. Less-Common Met. 174, 1273 1991CrossRefGoogle Scholar
12McGuiness, P.J., Zhang, X.J., Knoch, K.G.Harris, I.R.: HDDR hot-pressed magnets: Magnetic properties and microstructure. J. Magn. Magn. Mater. 104, 1169 1992CrossRefGoogle Scholar
13Ragg, O.M., Keegan, G., Nagel, H.Harris, I.R.: The HD and HDDR processes in the production of the Nd–Fe–B permanent magnets. Int. J. Hydrogen Energy 22(2–3), 333 1997CrossRefGoogle Scholar
14Gang, S., Lianxi, H., Bin, G.Xiudong, S.: Microstucture study on Nd2Fe14B/α-Fe nanocomposites during disproportionation and desorption- recombination. Mater. Sci. Forum 475–479, 2185 2005Google Scholar
15Gang, S., Lianxi, H.Erde, W.: Preparation and microstructure features of nanocrystalline Nd12Fe82B6 alloy powder by a joint technique combining mechanical milling with HDDR. Rare Met. Mater. Eng. 35(4), 609 2006Google Scholar
16Lianxi, H., Gang, S.Erde, W.: Mechanically activated disproportionation of NdFeB alloy by ball milling in hydrogen. Trans. Nonferrous Met. Soc. China 13(5), 1070 2003Google Scholar
17Shi, G., Hu, L.X., Wang, Z.R., Guo, B.Erde, W.: Phase and structural changes of Nd12Fe82B6 alloy during mechanical milling in argon and hydrogen atmosphere. J. Mater. Proc. Technol. 151, 258 2004CrossRefGoogle Scholar
18Book, D.Harris, I.R.: Hydrogen absorption/ desorption and HDDR studies on Nd16Fe76B8 and Nd11.6Fe82.3B5.9. J. Alloys Compd. 221(1–2), 187 1995CrossRefGoogle Scholar
19Hajime, N., Ken-ichi, K., Book, D., Sugimoto, S., Okada, M.Homma, M.: A thermodynamic study of the HDDR conditions necessary for anisotropic Nd–Fe–B powders in Proceedings of the 15th Workshop on Rare Earth Magnets and Their Applications Dresden, Germany,,1998 507–516Google Scholar
20Korst, W.L.Warf, J.C.: Rare earth-hydrogen system: Structural and thermodynamic properties. Inorg. Chem. 5, 1719 1966CrossRefGoogle Scholar