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Microstruoture-Property Relationships in Magenqubnch Magnets

Published online by Cambridge University Press:  25 February 2011

Raja K. Rishra
Raja K. Rishra*
Affiliation:
Physics Department, 0eneral Motors Research Laboratories, Warren, MI 48090-9055
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Abstract

Transmission electron microscopy has been used to characterize the microstructure of Nd-Fe-B magnets produced by melt-spinning and subsequent hot-pressing/die-upsetting. For a material of starting composition Nd.135Fe.815B.05, the basic microstructure od melt-spun, hot-pressed and dieupset magnets consists of two phases. In the optimally processed melt-spun ribbons and hot-pressed samples, small and randomly oriented Nd2Fe14B grains are surrounded by a thin noncrystalline Nd-rlch phase. The die-upset material consists of closely stacked flat Nd2Fe14B grains surrounded by a second phase of approximate composition Nd7Fe3. No Nd11Fe4B4 phase is observed in these materials, but it can form if the chemical composition and/or processing parameters are varied. In all these materials, Lorentz microscopy reveals that magnetic domain walls are pinned by the second phase. The differences in the hard magnetic properties of the three kinds of MAGNEQUENCH magnets closely correlate with the differences in the distribution of Nd2Fe14B crystallites and the pinning sites.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 96: Symposium F – High Performance Permanent Magnet Materials , 1987 , 83
Copyright
Copyright © Materials Research Society 1987

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