Microstructure of hot-pressed and die-upset NdFeB magnets
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), Vol. 62:3
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
IRON BORIDES
HOT PRESSING
MAGNETIC PROPERTIES
MICROSTRUCTURE
MAGNETS
NEODYMIUM BORIDES
ALIGNMENT
DIFFUSION
DOMAIN STRUCTURE
FCC LATTICES
GRAIN BOUNDARIES
GRAIN SIZE
MAGNETIZATION
BORIDES
BORON COMPOUNDS
CRYSTAL LATTICES
CRYSTAL STRUCTURE
CUBIC LATTICES
FABRICATION
IRON COMPOUNDS
MATERIALS WORKING
NEODYMIUM COMPOUNDS
PHYSICAL PROPERTIES
PRESSING
RARE EARTH COMPOUNDS
SIZE
TRANSITION ELEMENT COMPOUNDS
360204* - Ceramics
Cermets
& Refractories- Physical Properties