Directly quenched bulk nanocrystalline (Pr,Dy)-(Fe,Co)-B-Zr-Ti hard magnets

Piotr Pawlik 2Katarzyna Pawlik 2Hywel A. Davies 3Jerzy J. Wysłocki 2Waldemar Kaszuwara 1Nicola J. Harrison 3Iain Todd 3

1. Warsaw University of Technology, Faculty of Materials Science and Engineering (InMat), Wołoska 141, Warszawa 02-507, Poland
2. Institute of Physics, Częstochowa University of Technology, Al. Armii Krajowej 19, Częstochowa 42-200, Poland
3. University of Sheffield, Department of Engineering Materials, Mappin Street, Sheffield S1 3JD, United Kingdom

Abstract

The addition of 1 at.% of Zr to (Pr,Dy)x(Fe,Co)80-xB20 type alloys (x up to 4.5 at.%) led to significant improvement of their glass forming abilities, so that amorphous 1mm dia. rods and thin walled tubes having outer diameters up to 4 mm could be produced. Subsequent annealing of the amorphous samples resulted in formation of a nanocrystalline structure containing soft magnetic Fe3B, and the hard magnetic (Pr,Dy)2(Fe,Co)14B phases. However, the low concentration of the RE elements, together with the detrimental effect of Zr on the magnetic properties, resulted in relatively low values of coercivity JHc and of (BH)max for the alloys investigated. Recently, for as-cast Nd-Fe-B-type ribbon samples with Nd contents of ~9 at. % and high boron contents of ~15 at. %, significant coercivities were demonstrated. This has stimulated the present investigation of the processing of hard magnetic nanocrystalline bulk samples with improved magnetic properties. Nanocrystalline Fe-Co-Pr-B-Ti-Zr alloy rods of diameter 1 mm and tubes of outer diameter 3 mm, were produced by die casting. Good enhancement of remanence Jr to values>0.6Js, in combination with unusually high μ0 JHc of ~0.65T, were achieved for samples in the as-cast state. Subsequent annealing of the samples at various temperatures led to even better hard magnetic properties (i.e.μ0 JHc increased to ~1T for samples annealed at 300oC for 30 min).

Work supported by Polish Scientific Research Committee (KBN)(projects no. 3T08A 063 27 and 3T08C 008 28) and by the U.K. Engineering and Physical Sciences Research Council.

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Presentation: oral at E-MRS Fall Meeting 2005, Symposium B, by Piotr Pawlik
See On-line Journal of E-MRS Fall Meeting 2005

Submitted: 2005-05-18 10:58
Revised:   2009-06-07 00:44
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