Dresden 2003 – scientific programme
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MA: Magnetismus
MA 3: Magnetische Materialien
MA 3.9: Talk
Monday, March 24, 2003, 12:15–12:30, HSZ/401
HRTEM-studies of grain boundaries in die-upset Nd-Fe-Co-Ga-B magnets — •Anke Kirchner, Anke Kirchner, Jürgen Thomas, Oliver Gutfleisch, Dietrich Hinz, Karl-Hartmut Müller, Ludwig Schultz, Jürgen Thomas, Oliver Gutfleisch, Dietrich Hinz, Karl-Hartmut Müller, and Ludwig Schultz — Leibniz Institut of Solid State and Materials Research Dresden, PO Box 270016, 01171 Dresden, Germany
Highly texturized magnets from MQU-F material
(Nd13.6Fe73.6Ga0.6Co6.6B5.6) were produced by
die-upsetting. A remanence of Br = 1.39 T, a coercivity of
µ0jHc = 1.18 T and an energy product of (BH)max = 370 kJm−3
were obtained when using a relatively high degree of deformation (height
reduction: 80 %). Differential scanning calorimeter (DSC) measurements
reveal, beside an increase of the Curie temperature of the main phase a
substantial decrease of the melting point of the intergranular phase
(580∘C) in comparison to that of the ternary alloy MQP-A
(680∘C). The microstructure of hot deformed MQU-F material,
especially of the intergranular phase, was investigated by high resolution
transmission electron microscopy (HRTEM) and nano-EDX. A very homogeneous
distribution of the intergranular phase was observed. The Nd2Fe14B
crystals are surrounded by a Nd-rich phase, with a thickness of 0.4 to 2
nm. This phase is in an amorphous state. EDX analysis shows that the grain
boundaries are enriched in Nd and Ga and a small amount of Co was detected.