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Misch-Metal and/or Aluminum Substitutions in ND-FE-B Permanent Magnets

Published online by Cambridge University Press:  25 February 2011

B. M. Ma  and
C. J. Willzian
B. M. Ma
Affiliation:
Crucible Research Center, P. O. Box 88, Pittsburgh, PA 15230
C. J. Willzian
Affiliation:
Crucible Research Center, P. O. Box 88, Pittsburgh, PA 15230
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Abstract

The effects of misch-metal–and/or Al substitutions in the Nd-Fe-B alloy system have been investigated. Selected compositions were processed into magnets using the conventional powder metallurgy technique. As expected, misch-metal substitutions act to degrade the intrinsic magnetic characteristics and thus degrade the properties of the sintered magnet. It was observed that at a level of 25% of the total rare earth being comprised of misch-metal, energy products of the order of 25 MGOe were still able to be achieved. Processing of such material is difficult because higher sintering temperatures are required to fully densify the magnet, and the grain growth that occurs at these temperatures dramatically reduces the coercivity. The effects of misch-metal substitutions are quantified in this discussion.

Al was found to be beneficial for improving the coercivity in both the Nd-Fe-B and misch-metal-Fe-B alloy systems. Unfortunately Al substitutions reduce both the remanence and the Curie temperature. If the Al content is kept to 1 wt.% or less, magnets exhibiting reasonable properties can be made. Al doping as opposed to doping with expensive heavy rare earth elements such as Th or Dy is a less costly method of improving Hei, in the Nd-Fe-B magnets.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 96: Symposium F – High Performance Permanent Magnet Materials , 1987 , 133
Copyright
Copyright © Materials Research Society 1987

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References

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