HRTEM studies of grain boundaries in die-upset Nd–Fe–Co–Ga–B magnets
2003; Elsevier BV; Volume: 365; Issue: 1-2 Linguagem: Inglês
10.1016/s0925-8388(03)00661-3
ISSN1873-4669
AutoresA. Kirchner, J. H. Thomas, Oliver Gutfleisch, D. Hinz, Karin H. Müller, L. Schultz,
Tópico(s)Magnetic Properties and Applications
ResumoHighly textured magnets of MQU-F material (Nd13.6Fe73.6Ga0.6Co6.6B5.6) were produced by die-upsetting. A remanence Br=1.39 T, a coercivity μ0jHc=1.18 T and an energy product (BH)max=370 kJ m−3 were obtained when using a relatively high degree of deformation (height reduction: 80%). Differential scanning calorimetry measurements reveal, beside an increase of the Curie temperature of the main phase, a substantial decrease of the melting point of the intergranular phase (660 °C) in comparison to that of the ternary alloy MQP-A (680 °C). The microstructure of the hot-deformed MQU-F material, especially of the intergranular phase, was investigated by high-resolution transmission electron microscopy and energy dispersive X-ray spectroscopy (EDX) in the scanning transmission electron microscopic mode with a subnanometer probe. A very homogeneous distribution of the intergranular phase was observed. The Nd2Fe14B crystals are surrounded by an amorphous Nd-rich phase with a thickness of 0.4 to 2 nm. EDX analysis shows that the grain boundaries are enriched in Nd and Ga. Also, a small amount of Co was detected.
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