The effects of boron content on the microstructure and exchange coupling effect of Nd/sub 9.5/Fe/sub 85.5-x/B/sub 5+x/ melt spun ribbons

The magnetic properties, phases transformations and microstructural evolution of Nd/sub 9.5/Fe/sub 85.5-x/B/sub 5+x/(x=0, 1, 3 and 4) alloy ribbons have been investigated. Excellent magnetic properties with a Br=11.7 kG, iHc=6.6 kOe, (BH)max=18.7 MGOe and Br=11.4 kG, iHc=6.3 kOe, (BH)max=19 MGOe, can be achieved in the alloys with x=0 and 1, respectively, simply from direct quenching. For alloy ribbons with higher boron content (x=3 and 4), the magnetic properties degrade and are lower than that of the former even after subsequent annealing. From X-ray diffraction, TEM and magnetic analysis, the degradation of magnetic properties was found to result from the formation of Fe/sub 3/B phase inside Nd/sub 2/Fe/sub 14/B and /spl alpha/-Fe phases and to grain coarsening leading to the reduction of the exchange coupling effect between Nd/sub 2/Fe/sub 14/B and /spl alpha/-Fe or Fe/sub 3/B phases.