TOWARD LOW-ENERGY SPARK PLASMA SINTERING OF HOT-DEFORMED Nd-Fe-B MAGNETS

Abstract

In this work, we present a newly developed, economically efficient method
for processing rare-earth Nd-Fe-B magnets based on spark plasma sintering. It makes us
possible to retain the technologically essential properties of the produced magnet by
consuming about 30% of the energy as compared to the conventional SPS process. A magnet
with anisotropic microstructure was fabricated from MQU F commercial ribbons by low
energy consumption (0.37 MJ) during the deformation process and compared to the
conventionally prepared hot-deformed magnet, which consumed 3-times more energy (1.2
MJ). Both magnets were post-annealed at 650 °C for 120 min in a vacuum. After the postannealing
process, the low-energy processing (LEP) hot-deformed magnet showed a
coercivity of 1327 kAm-1, and remanent magnetization of 1.27 T. In comparison, the highenergy
processing (HEP) hot-deformed magnet had a coercivity of 1337 kAm-1 and a
remanent magnetization of 1.31 T. Complete microstructural characterization and detailed
statistical analyses revealed a better texture orientation for the HEP hot-deformed magnet
processed by high energy consumption, which is the main reason for the difference in
remanent magnetization between the two hot-deformed magnets. The results show that,
although the LEP hot-deformed magnet was processed by three times lower energy
consumption than in a typical hot-deformation process, the maximum energy product is only
8 % lower than the maximum energy product of a HEP hot-deformed magnet.