Microstructure and magnetic effects of small Cu additions to (Nd,Dy)FeB magnets

Journal Article · Tue Dec 31 23:00:00 EST 1996 · Scripta Materialia

DOI:https://doi.org/10.1016/S1359-6462(96)00312-0· OSTI ID:417803

Engelmann, H J ^[1]; Kim, A S ^[2]; Thomas, G ^[3]

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1. Inst. for Solid State and Materials Research Dresden (Germany)
2. Crucible Research, Pittsburgh, PA (United States)
3. Univ. of California, Berkeley, CA (United States). Dept. of Materials Science and Mineral Engineering

Sintered NdFeB magnets are characterized by excellent magnetic properties. The magnetic parameters are closely related to grain size, alignment, texture and distribution of second phases. Besides the influence of grain boundary phases there is also experimental evidence that small additions of non-ferromagnetic elements may improve the magnetic parameters. Ramesh et al. have reported that {sub j}H{sub c} increases sharply for small additions of Dy. It was shown that Dy partitions preferentially into the Nd{sub 2}Fe{sub 14}B phase. Furthermore, Ramesh et al. found that Dy replaces Nd in the hard magnetic Nd{sub 2}Fe{sub 14}B phase and Al segregates to interphase interfaces. Both of these effects result in an increase of coercivity due to a strong influence on the local magnetocrystalline anisotropy. These authors have also shown that the addition of Ho to NdFeB magnets results in the formation of spherical inclusions of rare earth oxides inside the Nd{sub 2}Fe{sub 14}B grains, which also contributes to an increase in intrinsic coercivity. These results confirm that evaluations of the microstructure are essential for understanding the magnetic properties of modified magnetic materials. The aim of the present research is to characterize the microstructure of (Nd,Dy)FeB magnets containing additions of Co, Nb and small amounts of Cu. Kim et al. have found that the combined addition of Co and Cu substantially increases the coercivity without any reduction in remanence and Curie temperature. The addition of Cu results in a considerable increase in {sub i}H{sub c}. An interpretation of this magnetic behavior will be given on the basis of the microstructural characterization.

• OSTI ID: 417803
• Journal Information: Scripta Materialia, Journal Name: Scripta Materialia Journal Issue: 1 Vol. 36; ISSN 1359-6462; ISSN SCMAF7
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
BORON ALLOYS
CHEMICAL COMPOSITION
COBALT ALLOYS
COPPER ADDITIONS
DYSPROSIUM ALLOYS
IRON ALLOYS
MAGNETIC PROPERTIES
MICROSTRUCTURE
NEODYMIUM ALLOYS
NIOBIUM ADDITIONS
TRANSMISSION ELECTRON MICROSCOPY
X-RAY DIFFRACTION