Spark Plasma Sintering Fe$_3$B–(Pr,Tb)$_2$Fe$_14$B Bulk Nanocomposite Permanent Magnets

In this paper, bulk nanocomposite permanent magnets are prepared by spark plasma sintering (SPS) technique using melt-spun powders with a nominated composition of Pr
_4.2
Tb
_0.3
Fe
₇₈
B
_17.5
. Effect of processing conditions on the density, microstructure, and magnetic properties of the magnets are studied. Higher sintering temperature improves the densification of the magnets, while deteriorates their magnetic properties simultaneously due to the excess crystal grain growth. An increased compressive pressure leads to better magnetic properties and higher density for the magnets. Magnet possesses a Br of 10.4 kGs and a Hci of 2.76 kOe under the optimal sintering condition. Observation shows the microstructure of the magnet contains fine grains with an average size of about 20 nm. The fine grain size in the microstructure and good magnetic properties are ascribed to the rapidly sintering speed and high compressive pressure of SPS, which effectively restrains the grain growth and allows the formation of fine crystalline materials with full dense in a short time