Hr. Madaah-hosseini et al., A correlation between intrinsic coercivity-electrical conductivity-thermaltreatment in a Nd11.9MM2.9Fe73.9Co3.3Ni1.1B6.9-type magnet, J ALLOY COM, 314(1-2), 2001, pp. 251-256
In this work, the effects of sintering temperature, cooling rate after sint
ering and post-sintering annealing treatments on the microstructure and mag
netic properties of a Nd11.9MM2.9Fe73.9Co3.3Ni1.1B6.9-type magnet have been
investigated. It was found that the best magnetic properties were only obt
ained at a narrow range of sintering temperature at 1333-1353 K. Porosity w
as found to be minimized with increasing sintering temperature up to 1333 K
. However, some grain growth occurred by increasing the sintering temperatu
re from 1333 to 1353 K. Further increase of sintering temperature resulted
in a significant decrease in the magnetic properties due to appearance of o
r-iron in the microstructure of the magnets and/or grain growth. The depend
ence of intrinsic coercivity (H-cJ) on the cooling rate (after sintering) a
nd post-sintering annealing treatments has been related to electrical condu
ctivity (EC) of the magnets; thus an increase in the EC resulted in a signi
ficant improvement in the H-cJ values. This could be due to reduction of re
sidual stresses within the specimens during slow cooling after sintering/po
st-sintering annealing treatments. The compatibility between the variations
of the H-cJ and EC with the cooling rates (after sintering) or a post-sint
ering annealing treatment at around 873 K confirms this mater. (C) 2001 Els
evier Science B.V. All rights reserved.