Microstructural and magnetic studies of cast and annealed Nd and PrFeCoBZr alloys 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 been assessed using a permeameter technique. HDDR powders from the alloy in the as-cast and annealed (1100°C for 20 h) conditions were isostatically pressed and bonded in wax before testing. It has been shown that it is possible to produce highly anisotropic HDDR material from the Pr13.7Fe63.5Co16.7B6Zr0.1 alloy in the annealed state, whereas the corresponding Nd13.7Fe63.5Co16.7B6Zr0.1 HDDR material prepared under the same conditions, did not exhibit any significant permanent magnetic properties. The microstructures of both as-cast and annealed alloys have been investigated by scanning electron microscopy and energy dispersive X-ray analysis in an attempt to reveal the reason for this behaviour. Thermomagnetic analysis using in-situ magnetisation measurements have also been carried out on the alloys.