SYNTHESIS OF EXCHANGE COUPLED BULK COMPOSITE HARD MAGNETS VIA HOT ISOSTATIC PRESSING AND EXTRUSION

摘要

Hot isostatic pressing (HIP) and extrusion processing were used to synthesize exchange coupled composite magnetic structures. Magnets were processed from a mixture of micrometer size magnetically hard (SmCo or NdFeB) and nanometer size magnetically soft (FeCo) constituents. Hot isostatically pressed magnets revealed "constricted" type hysteresis loops. Also, coercivities were reduced with the increased amount of soft phase for these HIP'ed magnets. Extruded magnets on the other hand exhibited magnetic properties that are strongly dependent on the extrusion direction. In the extruded NdFeB+FeCo case, the hysteresis loops taken with the applied field parallel to the extrusion direction indicated uncoupled two-phase behavior as a step in the demagnetization curve. The same magnet showed completely coupled behavior when measured with an applied field direction perpendicular to the extrusion direction. In this manuscript we document our processes and interim results of our research effort to develop exchange coupled bulk permanent magnets.