Search

The use of high-remanence rapidly solidified Nd-Fe-B alloys as a starting material for die-upset magnets was investigated. The results showed that remanence increased along with the die-upset (DU) level and reached a maximum of 13.5 kG at 70% DU for ternary Nd-Fe-B magnets. Nonuniform deformation also had a detrimental effect on remanence. The decreased coercivity can be offset by heat treatments, dysprosium substitutions and low-level additives.

Microstructures of GdxAg100-x alloy ribbons prepared by melt spinning are examined by x-ray diffraction and transmission electron microscopy to evaluate their magnetic and magneto-caloric characteristics. The Gd-only ribbons exhibit a single field-induced entropy change (Delta-S) peak near 280 K. Delta-S shows another peak in the 100-120 K range for GdxAg100-x alloys, indicating an amorphous, ferromagnetic Gd-Ag component. The Gd50Ag50 ribbons comprise antiferromagnetic crystalline GdAg.

Studies of phase formation in melt-spun Nd-Fe-Mo-Ti alloys at different quench rates and quench wheel surface velocities show that slow quench velocity facilitates ThMn(12)-type crystal structure development while high wheel velocities result in the TbCu(7)-type structure. The stability of the ThMn(12) structure is higher at the Mo-rich end than at the Ti-rich end, indicating that compositions at the Ti-rich end are more susceptible to quenching. Heat treatments of alloys show that annealing temperatures higher than 1,000 degrees centigrade are essential for ThMn(12) crystal structure formation.