Microstructural and magnetic studies of cast and annealed Nd and PrFeCoBZralloys and HDDR materials

The magnetic properties of HDDR permanent magnets prepared from alloys with a nominal composition of RE13.7Fe63.5Co16.7B6Zr0.1 (RE: Pr and Nd) have be en assessed using a permeameter technique. HDDR powders from the alloy in t he as-cast and annealed (1100 degrees C for 20 h) conditions were isostatic ally pressed and bonded in wax before testing. It has been shown that it is possible to produce highly anisotropic HDDR material from the Pr13.7Fe63.5 Co16.7B6Zr0.1 alloy in the annealed state, whereas the corresponding Nd13.7 Fe63.5Co16.7B6Zr0.1 HDDR material prepared under the same conditions, did n ot exhibit any significant permanent magnetic properties. The microstructur es of both as-cast and annealed alloys have been investigated by scanning e lectron microscopy and energy dispersive X-ray analysis in an attempt to re veal the reason for this behaviour. Thermomagnetic analysis using in-situ m agnetisation measurements have also been carried out on the alloys. (C) 200 0 Elsevier Science S.A. All rights reserved.