The ability to vary the composition of NdFeB-type magnets, during or after
the milling stage offers a number of advantages. To this end, powder blendi
ng processes have been det eloped. In the present work. the sintering chara
cteristics of a Nd13Fe80.5B6.5 alloy have been improved by powder blending
with neodymium hydride, A blending addition of 1 at% of neodymium in the fo
rm of Nd-hydride, consistent with a final composition of Nd14Fe79.6B6.4, wa
s sufficient to reduce the required sintering temperature from 1130 to 1070
degreesC, with a resultant improvement in the coercivity due to less grain
growth and better grain isolation. The addition of dysprosium hydride to a
Nd14Fe79B7 alloy by blending resulted in a further enhancement of the coer
civity, a 2 at% addition yielding an approximate doubling in the value of i
ntrinsic coercivity. Examination of the microstructure of dysprosium-hydrid
e blended magnets showed the dysprosium to be concentrated in the outer reg
ions of the matrix grains, with the centres being essentially dysprosium-fr
ee. Hydrogen has also been employed in improving the milling characteristic
s of the high melting point elements niobium and vanadium. Fine powders of
niobium and vanadium hydride were prepared acid were successfully blended i
nto magnets with an even distribution throughout the microstructure. These
studies have shown that powder blending of metal hydrides is an effective w
ay of both promoting liquid-phase sintering in low rare earth composition m
agnets and of modifying the grain boundary phases and hence the magnetic pr
operties. (C) 2001 international Association for Hydrogen Energy. Published
by Elsevier Science Ltd. All rights reserved.