The microstructure of hot formed neodymium–iron–boron magnets with energy product 48 MG Oe

Melt-spun Nd–Fe–B ribbons containing small amounts of Co, Ga, and C were die upset to 60% and 70% reduction in height in an argon atmosphere between 750 and 800 °C. The magnet, which was die upset 70%, has a remanence of 14.2 kG, Hci of 14.8 kOe, and (BH)max of 48 MG Oe. The interior of the magnet consists of well-aligned Nd2Fe14B grains separated by a Nd-rich intergranular phase. Intermixed with such aligned grains, we observed zones of unaligned fine-grained material without any intergranular phase. Since the intergranular phase is a key factor for deformation and alignment and it is uniformly distributed in the hot pressed precursor, it will be possible to enhance the alignment further by controlling the redistribution of the intergranular phase during die upsetting.