HIGH-REMANENCE RAPIDLY SOLIDIFIED ND-FE-B - DIE-UPSET MAGNETS

The best starting materials for die-upset magnets are moderately overq uenched melt-spun ribbons of Nd-Fe-B alloys with approximately 20 at. % more rare earth than stoichiometric Nd2Fe14B. Remanence increases wi th increasing die-upset (DU) level, reaching a maximum of 13.5 kG at 7 0% DU for ternary Nd-Fe-B magnets, beyond which cracking limits perfor mance. Remanence is also limited by nonuniform deformation, particular ly for moderately die-upset magnets. Heat treatments, dysprosium subst itutions, or low-level additives can be used to compensate for the dec reases in coercivity which accompany increases in die-upset level. By die upsetting in stages and removing misaligned surfaces, a large Nd-F e-Co-B-Ga magnet (approximately 30 g) has been produced with both a hi gh remanence (14.2 kG) and a high-energy product (48.5 MG Oe).