The effect of hydrogen pressure on the kinetics of the HDDR-process of bulk Nd-Fe-B-type alloys

Author

Gutfleisch, Oliver ; Short, Carolyn ; Verdier, Marc ; Harris, Ivor Rex

Author_Institution

Sch. of Metall. & Mater. Sci., Birmingham Univ., UK

Volume

30

Issue

2

fYear

1994

fDate

3/1/1994 12:00:00 AM

Firstpage

642

Lastpage

644

Abstract

The HDDR (hydrogenation, disproportionation, desorption, recombination)-process of bulk Nd-Fe-B-type alloys has been investigated by in-situ electrical resistivity measurements. The effect of hydrogen pressure on the rate of the disproportionation reaction, in which the Nd ₂Fe₁₄B phase forms Fe, Nd-hydride and Fe₂B, was studied in detail on a Nd_14.68Dy_0.94Al_0.62Fe_76.47Nb _0.5B_6.79 alloy, which is used for the production of commercial permanent magnets. Experimental data reveal a strong dependence of the HDDR-kinetics on the hydrogen pressure which was varied between p(H₂)=0.1-1.0 bar at T=750°C. Optical micrographs suggest that the Nd-rich grain boundary phase acts as a diffusion path for the hydrogen in the HDDR-process. The 2-14-1 matrix phase subsequently disproportionates from the grain boundary phase inwards

Keywords

aluminium alloys; boron alloys; desorption; dysprosium alloys; electrical conductivity measurement; electrical conductivity of crystalline metals and alloys; ferromagnetic properties of substances; grain boundary diffusion; hydrogen; iron alloys; neodymium alloys; niobium alloys; permanent magnets; H pressure; HDDR-process; Nd_14.68Dy_0.94Al_0.62Fe_76.47Nb_0.5B_6.79; Nd₂Fe₁₄B; desorption; diffusion path; disproportionation; electrical resistivity; grain boundary phase; hydrogenation; optical micrographs; permanent magnets; recombination; Aluminum alloys; Electric resistance; Electric variables measurement; Grain boundaries; Hydrogen; Iron alloys; Kinetic theory; Neodymium; Niobium alloys; Production;

fLanguage

English

Journal_Title

Magnetics, IEEE Transactions on

Publisher

ieee

ISSN

0018-9464

Type

jour

DOI

10.1109/20.312362

Filename

312362