Title :
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
fDate :
3/1/1994 12:00:00 AM
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 Fe2 B, was studied in detail on a Nd14.68Dy0.94Al0.62Fe76.47Nb 0.5B6.79 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; Nd14.68Dy0.94Al0.62Fe76.47Nb0.5B6.79; 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;
Journal_Title :
Magnetics, IEEE Transactions on
