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Author Branagan, D. J. ♦ Dennis, K. W. ♦ Kramer, M. J. ♦ McCallum, R. W.
Source United States Department of Energy Office of Scientific and Technical Information
Content type Text
Language English
Subject Keyword MATERIALS SCIENCE ♦ MAGNETIC MATERIALS ♦ MICROSTRUCTURE ♦ NEODYMIUM BORIDES ♦ MAGNETIC PROPERTIES ♦ IRON BORIDES ♦ PERMANENT MAGNETS ♦ CRYSTALLIZATION ♦ SOLUBILITY ♦ PHASE STUDIES
Abstract In bulk permanent magnets, the extrinsic properties relating to the microstructure determined the level of hard magnetic properties that is actually achieved. Many researchers have worked on the microstructure property relationships in the Nd{sub 2}Fe{sub 14}B (2-14-1) system but, in general, the approach has been to analyze the microstructure of materials which have been shown to have good magnetic properties rather than to study the effect of alloy additions on the metallurgical properties of the system. The microstructure which is obtained under a given set of processing conditions is highly dependent on the solidification behavior of the alloy, as well as grain growth phenomena. Alloy additions which effect the solidification behavior of the melt and then form precipitates which pin grain boundaries, and therefore control grain size, should be valuable in producing the uniform microstructure required for good magnetic properties. A number of refractory metal carbides perform both of these functions. The carbides have a reasonable degree of solubility in the 2-14-1 melt and, under conditions of reasonable rapid solidification, a degree of metastable solubility in the 2-14-1 phase. However, there is very limited equilibrium solid solubility in the 2-14-1 phase so that the intrinsic magnetic properties are not effected. The addition of these materials to 2-14-1 results in a factor or three reduction of the quench rate required to produce amorphous material. In addition, the crystallization temperature of the glass is enhanced leading to enhance nucleation and finer grain size during crystallization. Finally refractory metal carbide precipitates decorate the grain boundaries of the crystallized material inhibiting grain growth. Transition metal carbide formation, solid and liquid solubility, effects on solidification, nucleation, and grain growth will be discussed. {copyright} {ital 1996 American Institute of Physics.}
ISSN 00218979
Educational Use Research
Learning Resource Type Article
Publisher Date 1996-04-01
Publisher Department Ames National Laboratory
Publisher Place United States
Journal Journal of Applied Physics
Volume Number 79
Issue Number 8
Technical Publication No. CONF-951101-
Organization Ames National Laboratory


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