Microstructure of hot-pressed and die-upset NdFeB magnets

Journal Article · Sat Aug 01 04:00:00 EDT 1987 · J. Appl. Phys.; (United States)

DOI:https://doi.org/10.1063/1.339709· OSTI ID:6423161

Mishra, R K

Transmission electron microscopy was used to establish densification, alignment, and magnetization reversal mechanisms in hot-pressed and die-upset NdFeB magnets. Microstructures of these materials reveal two principal phases: Nd/sub 2/Fe/sub 14/B grains and a grain boundary phase of approximate composition Nd/sub 7/Fe/sub 3/. The grains in the hot-pressed material are polygonal and isotropic, while those in the die-upset material are flat platelets. The alignment of die-upset magnets arises exclusively from the fact that hot deformation produces platelets of Nd/sub 2/Fe/sub 14/B grains with their c axes parallel to the stress axis. It is argued that yielding plays an important role in the densification of the hot-pressed samples, and diffusion slip is critical to the alignment. The grain boundary phase appears as a crystalline or noncrystalline phase in the hot-pressed samples but has an fcc structure in the die-upset samples. Magnetic domain walls are shown to be pinned at the grain boundary phase in both cases. A Nd-rich spongy phase is observed to form at the boundaries where two ribbons fuse, but has no significance for the magnetic properties.

• Research Organization: Physics Department, General Motors Research Laboratories, Warren, Michigan 48090-9055
• OSTI ID: 6423161
• Journal Information: J. Appl. Phys.; (United States), Journal Name: J. Appl. Phys.; (United States) Vol. 62:3; ISSN JAPIA
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360204* -- Ceramics
Cermets
& Refractories-- Physical Properties
ALIGNMENT
BORIDES
BORON COMPOUNDS
CRYSTAL LATTICES
CRYSTAL STRUCTURE
CUBIC LATTICES
DIFFUSION
DOMAIN STRUCTURE
FABRICATION
FCC LATTICES
GRAIN BOUNDARIES
GRAIN SIZE
HOT PRESSING
IRON BORIDES
IRON COMPOUNDS
MAGNETIC PROPERTIES
MAGNETIZATION
MAGNETS
MATERIALS WORKING
MICROSTRUCTURE
NEODYMIUM BORIDES
NEODYMIUM COMPOUNDS
PHYSICAL PROPERTIES
PRESSING
RARE EARTH COMPOUNDS
SIZE
TRANSITION ELEMENT COMPOUNDS