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Room: Salon 8
Location: Clarion Plaza Hotel
Session Chairpersons: KNona C. Liddell, Department of Chemical Engineering, Washington State University, Pullman, WA 99164; Garry W. Warren, Department of Metallurgical and Materials Engineering, University of Alabama, Tuscaloosa, AL 35487
RECENT DEVELOPMENTS IN RARE-EARTH-BASED ADVANCED PERMANENT MAGNET MATERIALS: FACTORS AFFECTING ACQUISITION AND STABILITY OF COERCIVITY: L.H. Lewis, Materials Science Division, Department of Applied Science, Bldg. 480, Brookhaven National Laboratory, Upton, NY 11973-5000, C.H. Sellers, Idaho National Engineering Laboratory, Lockheed Idaho Technologies Co., Idaho Falls, ID 83415-2211, V. Panchanathan, Magnequench International, Inc., 6435 Scatterfield Road, Anderson, IN 46013
The basic relationships that link the microstructural properties of advanced permanent magnet materials to the magnetic hysteretic properties such as the magnetic hysteretic properties such as the coercivity are subtle and often
difficult to quantify. These difficulties are magnified when the magnetic materials are fabricated by methods such as rapid solidification, which has the potential to produce non-equilibrium phases and structures in a nano-scaled matrix.
Nd-Fe-B POWDERS FOR BONDED MAGNETS--AN OVERVIEW: V. Panchanathan, Magnequench International, Inc., 6435 Scatterfield Road, Anderson, IN 46013
The rapidly solidified Nd-Fe-B powders form the entire basis of the bonded magnet industry. At present the rapid solidification is carried out exclusively by melt spinning, a technique in which a stream of molten alloy is directed onto the outer surface of a rapidly spinning wheel, producing flake like particles having highly stable and magnetically hard microstructure. These particles are comminuted into powder before being processed into bonded magnets. These powders are magnetically isotropic. These powders are magnetically isotropic. The bonded magnets made using these powders range in energy product of 5 MGOe for injection molded magnets to about 12 MGOe for compression molded varieties.
MAGNETISATION MECHANISMS IN EXCHANGE COUPLED MAGNETS: R. Street, Research Centre for Advanced Mineral and Materials Processing, The University of Western Australia, Nedlands, WA 6907, Australia
Nanocrystalline composites containing grains of hard (typically RE/TM alloys) and soft (typically -Fe) magnetic materials exhibit the commercial useful property of remanence enhancement. The modelling of remanence enhancement in terms of inter- and intra- grain magnetic exchange coupling will be explained. The results of measurements of the magnetic properties of Nanocrystalline remanence enhanced magnets prepared by mechanochemical and melt quenching processes will be described.
10:00 am BREAK
RARE EARTH-BASED GIANT MAGNETOSTRICTIVE MATERIALS: S.F. Cheng, Naval Surface Warfare Center, Silver Spring, MD 20903; A.E. Clark, Clark Associates, Adelphi, MD 20783
Among the many extraordinary features of the rare earths are their magnetic and magnetoelastic properties. The rare earths, e.g., Tb, Dy, Nd, Sm, are known worldwide for their large magnetocrystalline anisotropy and magnetization, which has led to the importance of magnetic rare earths as vital ingredients of modern permanent magnets. In this paper, we focus on the strain dependence of these giant effects which gives rise to huge magnetostrictions, magnetomechanical couplings, and E effects. Magnetostrictions greater than 10-3 have been measured at temperatures as high as 250°C. At low temperatures Magnetostrictions reaches ~10. No other solid state material can match these values.
AQUEOUS CORROSION STUDY OF RAPIDLY SOLIDIFIED NdFeB PERMANENT MAGNETS WITH TiC ADDITIONS: M. Arenas, G.W. Warren, Department of Metallurgical & Materials Engineering, University of Alabama, Tuscaloosa, AL 35487, C.P. Li, K.W. Dennis, and R.W. McCallum, Dept. of Materials Sci. & Engineering, Iowa State Univ., Ames Laboratory, Ames, IA 50011
A corrosion study of a bonded NdFeB permanent magnet material alloyed with titanium carbide additions has been undertaken. Bonded magnets produced by rapid solidification of the alloy and consolidation in a polymer matrix are
attractive due to lower cost, greater durability, and useful shape-forming ability. Melt spinning is used to produce ribbons of the desired composition. The ribbons are formed by the ejection of molten alloy onto the surface of a rotating wheel. The samples tested were ribbons of different composition and wheel speed. Commercial epoxy was used as a bonding medium.
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