DIE-UPSET ND-FE-CO-B MAGNETS FROM BLENDS OF DISSIMILAR RIBBONS

We prepared die-upset Nd-Fe-Co-B magnets from melt-spun ribbon powders which were a series of blends of two ribbon alloys. One alloy was always ternary Nd-Fe-B (no cobalt), and in the other cobalt replaced up to half of the iron. Differential scanning calorimeter measurements revealed that during hot working, the cobalt diffused across ribbon boundaries, effectively redistributing the transition metal concentration throughout the magnet. Instead of anomalies indicating the Curie temperatures of the two original ribbon compositions, we found a single transition consistent with the average cobalt concentration in the magnet. However, the transition was broader than expected, suggesting that the homogenization was incomplete. These results are new evidence of massive diffusion occurring between ribbons, changing the microstructure and facilitating the deformation of the otherwise rigid 2-14-1 magnet.