Lean neodymium Nd-Fe-B magnets containing minor addition of titanium

Marzena Spyra 1Daniela Derewnicka 2Marcin Leonowicz 1

1. Warsaw University of Technology, Faculty of Materials Science and Engineering (InMat), Wołoska 141, Warszawa 02-507, Poland
2. Institute of Precision Mechanics, Duchnicka 3, Warszawa 01-796, Poland

Abstract

The effect of titanium addition on the structure and magnetic properties was studied for nanocomposite Nd7Fe79-xB14Tix and Nd8Fe78-xB14Tix systems. The alloys were rapidly solidified by melt-spinning with the roll speed of 20 m/s. The overquenched, amorphous ribbons were subsequently crystallization annealed at 680-700 ºC for 20 min. It was found that addition of 2 and 4 at% of Ti leads to substantial increase of the coercivity and maximum energy product of the nanocomposite magnets while maintaining the remanence unchanged. The highest properties were obtained for the alloys containing 4 at% of Ti. The maximum energy product of 122 kJ/m3 was obtained for the Nd8Fe74B14Ti4 alloy. The x-ray phase analysis revealed a presence of the hard magnetic Nd2Fe14B and soft magnetic phases (Fe, Fe2B) in all the alloys studied. For the alloys containing Ti additional boride phases, such as: TiB2 could also be detected. More detailed information on the phase constitution was obtained from the Mössbauer spectroscopy. Comparison of the Ti-free and 4 at% Ti alloys revealed that the amount of the hard magnetic Nd2Fe14B phase grows up from 66,60% to 82,82% for Nd8Fe78-xB14Tix system and decreases from 84,53 % to 69,88% for the Nd7Fe79-xB14Tix system. The TEM studies showed substantial differences in the morphology of the alloys. The NdFeB alloys contain grains of various sizes about hundred nanometers. The alloys containing 4 at% of Ti exhibit more homogeneous structure with the crystal sizes of up to 40 nm.

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Presentation: Poster at E-MRS Fall Meeting 2009, Symposium H, by Daniela Derewnicka
See On-line Journal of E-MRS Fall Meeting 2009

Submitted: 2009-05-27 09:40
Revised:   2009-06-07 00:48
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