Search

Pr-Fe-B die-upset magnets exhibited a lower remanence and a higher coercivity than analogous Nd-Fe-B magnets, with the microstructure of both magnets exhibiting similarities. Enhanced magnetic domain wall pinning and increased coercivity in Pr-Fe-B magnets was due to the thick intergranular phase. Hot-worked Pr2Fe14B magnets were obtained from melt-spun ribbons.

Die upsetting melt-spun ribbons of hot-pressed Pr-Co and Sm-Co pressure alloys produce the magnetically anisotropic PrCo5 type of magnets. Magnetic coercivity improves on low-level carbon addition to the alloys. Whereas increased carbon addition maximizes coercivity and drastically reduces magnetic remanence, PrCo5 type magnets have a higher saturation magnetization phase and substituting Sm for Pr and Fe for Co which would greatly improve the magnet's coercivity and remanence.

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.

The characteristics of crystallographic alignment of anisotropic magnetic materials made from die-upset Nd2Fe14B materials were investigated using x-ray diffraction spectra analysis. The observed spectra allowed alignment factors to be determined by comparison of the actual intensity shifts to reference intensity shifts that come with crystallographic alignment. The results showed that the method was effective in quantifying crystallographic alignment.

The dependence of the magnetostriction, mechanical hardness and density on processing parameters on the SmFe(sub2) volume fill fraction and consolidation temperature is reported. Magnetostriction rises monotonically with rising SmFe(sub2) content, although density and hardness decrease. Hot pressed SmFe(sub2) powder has high porosity and does not register on the Rockwell B hardness scale, but low fill fraction composites are within 10% of theoretical density, having a hardness of 40-85 Rockwell B. A good combination of properties is between 40-60% SmFe(sub2).

Differential scanning calorimetric estimations of the Curie temperatures of cobalt and iron diffusion in die-upset Nd-Fe-Co-B-magnets from metal-spun ribbons reveal a marked diffusion between ribbons that cause microstructure alteration and the deformation of the rigid 2-14-1 magnet. Cobalt diffuses across ribbons during hot working to rearrange the transition metal accumulation over the magnet. Homogenization of the metal composition is, however, not thorough.

Melt spinning of rare-earth cobalt alloys yields ribbons which have the hexagonal PrCo5 phase as the major phase. Consolidation of these ribbons at very high pressures and temperatures yields fully-dense hot-pressed magnets with isotropic magnetic properties. Nearly 75% saturation magnetization is exhibited by these magnets.