Effect of Ti and C additions on the microstructure and magnetic properties of Nd6Pr1Fe80B13 melt-spun ribbons

We have investigated the microstructure of Nd6Pr1Fe80−xTixB13−yCy (x = 0, 4; y = 0, 1) melt-spun ribbons using transmission electron microscopy (TEM) and three dimensional atom probe (3DAP) analysis to correlate their hard magnetic properties with the microstructure. Optimally quenched and annealed Nd6Pr1Fe76B12Ti4C1 ribbon, which was composed of Nd2Fe14B grains of about 16 nm mean diameter separated by Fe3B grain boundary phase, showed a maximum energy product of 112 kJ/m3 with coercivity of 510 kA/m. The addition of 4 at.% Ti significantly modified the solidification path by suppressing the formation of Nd2Fe23B3 phase and promoting the formation of Nd2Fe14B phase. TEM observations showed that the additions of Ti and C refined the microstructure, and 3DAP analysis indicated that the formation of TiC at the Nd2Fe14B grain boundary is the reason for the refined grain size and enhanced remanence.