Magnetic materials based on the transition metal-rare earth-(boron, carbon) alloys

Thesis/Dissertation · Thu Jan 01 00:00:00 EST 1987

OSTI ID:6511984

Liu, N C

The potential of iron-rare earth-carbon-boron alloys for generating case permanent magnets that do not require secondary processing such as powder metallurgy or melt spinning was explored. In bulk-alloys, intrinsic coercivities above 12 KOe can be obtained when the magnetically hard phase, tetragonal Fe/sub 14/R/sub 2/X (R = rare earth elements, X = boron, carbon, or a mixture of both) does not crystallize directly from the melt. Higher coercivities are based on a unique microstructure consisting of cells of Fe/sub 14/R/sub 2/X one to a few ..mu..m in diameter. To understand the effect of composition and temperature upon phases and microstructures produced, a systematic study of Fe-R-B-C alloys was undertaken, in which rare earth metals R consisted of Y, La, Ce, Pr, Nd, Sm, Gd, Dy, and Er. The tetragonal carbide Fe/sub 14/R/sub 2/C has the same crystal structure as Fe/sub 14/Nd/sub 2/B (phi phase) and is stable when R = Gd, Dy, Er. The phi/sub 2/ phase does not exist in alloys Fe-R-C with R = light rare earths. However, one tenth of C replaced by B can stabilize the phi/sub 2/ phase in these alloys. The lattice constant a of this tetragonal phase decreases slightly and c decreases about 1% as the C fraction increases from zero to 1. The cell size remains at one to a few ..mu..m without coarsening even under annealing at 900/sup 0/C/72 h. Most of the cells are a single magnetic domain, and the domain walls are trapped at the cell boundaries. Contrary to the sintered Fe-Nd-B magnets, pulverized specimens of this alloy retain their high /sub 1/H/sub c/.

• Research Organization: North Carolina State Univ., Raleigh (USA)
• OSTI ID: 6511984
• Resource Relation: Other Information: Thesis (Ph. D)
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
BORON ALLOYS
MAGNETIC PROPERTIES
CARBON ADDITIONS
IRON ALLOYS
PERMANENT MAGNETS
MAGNETIC MATERIALS
RARE EARTH ALLOYS
COERCIVE FORCE
LATTICE PARAMETERS
MICROSTRUCTURE
PHASE STUDIES
ALLOYS
CRYSTAL STRUCTURE
MAGNETS
MATERIALS
PHYSICAL PROPERTIES
360104* - Metals & Alloys- Physical Properties
360102 - Metals & Alloys- Structure & Phase Studies