Characterization of Rare Earth Permanent Magnets

Conference · Sat Jun 01 04:00:00 EDT 1991

OSTI ID:5412797

Huetten, A. ^[1]; Thomas, G. ^[1]

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1. University of California, Berkeley, CA (United States); Lawrence Berkeley Laboratory (LBL), Berkeley, CA (United States)

Recently developed alloys based either on ternary phases such as Nd₂Fe₁₄B (2-14) or on iron-rich pseudobinaries with the ThMn₁₂-structure combine excellent intrinsic magnetic properties with the appropriate microstructure for applications as hard magnetic materials. In order to understand the magnetic behavior of these materials, systematic microstructural characterization has been performed using microdiffraction, x-ray microanalyses and high resolution electron microscopy. The magnetic behavior of three types of NdFeB specimens, namely sintered, mechanically alloyed and melt-spun, is correlated to their microstructure. The effect of minority phases on the magnetization and the coercivity in these materials is investigated. The ease with which the nonmagnetic Nd-rich grain boundary phase decouples hard magnetic "2-14" matrix grains depends on their average grain size which is related to the different preparation processes. The appearance of the nonmagnetic B-rich phase which acts as a source of local demagnetization fields is also a function of the preparation methods and can be avoided by rapid solidification. In the SmFeMo-alloys the hard magnetic phase is tetragonal with the ThMn₁₂-structure which has about the same intrinsic magnetic properties as the "2-14". Although there are no intergranular phases in the 1-12 alloys, Sm-oxides become important as minority phases in these magnets. In comparison, SmFeTi-specimens have higher coercivities, and the origin of this is investigated as to whether any other hard magnetic phase besides 1-12 exists.

• Research Organization: Lawrence Berkeley Laboratory (LBL), Berkeley, CA (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Basic Energy Sciences (BES). Materials Sciences & Engineering Division (MSE); Alexander von Humboldt Foundation
• DOE Contract Number: AC03-76SF00098
• OSTI ID: 5412797
• Report Number(s): LBL--29553; CONF-901059--1; ON: DE91017010
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360102* -- Metals & Alloys-- Structure & Phase Studies
360104 -- Metals & Alloys-- Physical Properties
ALLOYS
ANNEALING
BORON ALLOYS
COLD WORKING
CRYSTAL STRUCTURE
ELECTRON MICROSCOPY
FABRICATION
GRAIN SIZE
HEAT TREATMENTS
INTERMETALLIC COMPOUNDS
IRON ALLOYS
IRON BASE ALLOYS
MAGNETIC PROPERTIES
MAGNETS
MATERIALS WORKING
MICROSCOPY
MICROSTRUCTURE
NEODYMIUM ALLOYS
PERMANENT MAGNETS
PHYSICAL PROPERTIES
RARE EARTH ALLOYS
SAMARIUM ALLOYS
SINTERING
SIZE
TITANIUM ALLOYS
TRANSMISSION ELECTRON MICROSCOPY