High-performance alpha-Fe/Pr2Fe14B-type nanocomposite magnets produced by hot compaction under high pressure

The alpha-Fe/R2Fe14B-type nanocomposite magnets have been prepared by hot p ressing melt spun Pr8Dy1Fe74.5Co10Nb0.5B6 flakes under a conventional press ure P of 125 MPa and high pressures ranging from 1 to 7 GPa. It was found t hat increasing compaction pressure from 125 MPa to 5 GPa led to marked grai n refinement in the magnet and consequently resulted in significant improve ment of magnetic properties. When hot pressing under even higher pressure ( P > 5 GPa), however, the crystallization was constrained and the hot presse d magnets retained a certain amount of amorphous phase besides the Pr2Fe14B -type phase and alpha-(FeCo) phase, which resulted in the deterioration of the magnetic properties. A remanence of 11.1 kG, coercivity of 10.2 kOe, an d maximum energy product of 23.6 MGOe have been achieved in the magnet hot pressed under a pressure of 5 GPa. (C) 2000 American Institute of Physics. [S0021-8979(00)02513-5].