Abstract: A method is provided for forming rare earth-transition metal (RE-TM) powders directly into radially aligned, thin, curved permanent magnets supported on ferromagnetic backings. Such magnets are particularly suited for use as D.C. motor pole pieces. In the method, a powder cavity is formed between a ferromagnetic backing layer and a composite forming mandrel. The mandrel has a ferromagnetic core slidably retained in a thin magnetic sleeve. The powder in the cavity is pressed in a magnetic field to a density of about 50%. Thereafter, the core of the mandrel is first removed and then the nonmagnetic sleeve. After both mandrel sections are withdrawn, the powders are maintained in the magnet shape for further processing by mechanical interlocking of the particles, and the magnet shape itself is magnetically attracted to the backing layer by the residual magnetism of the powder. The mass may be heated to coalesce the powder and bond it to the backing.

Abstract: In a preferred embodiment thin curved rare earth-cobalt magnets supported on the interior surface of a steel casing are formed by hot isostatic compaction. Rare earth-cobalt powder is magnetically aligned and compacted to at least 65% of the theoretical density. The relatively strong, curved green compacts are positioned on a curved mandrel and placed in a closely fitting steel casing which is evacuated and sealed. The magnets are densified under isostatic gas pressure at elevated temperatures and bonded to the steel. The steel backing serves as an integral motor casing when such magnets are used in D.C. motors.

Abstract: Self-supporting magnets, suitable for use as pole pieces of D.C. motors, are made from rare earth-transition metal powders which are pressed into thin, curved shapes and radially magnetically aligned. The compacts are restrained during sintering between special dies shaped to prevent them from warping without inhibiting circumferential or radial shrinkage.

Abstract: In a preferred embodiment, thin curved rare earth-transition metal (RE-TM) compacts with good green strength are made by a stepwise process in the molding cavities of a portable compacting tooling. The powder is partially compacted and magnetically aligned in a first press equipped with magnetizing means. It is then transported in the tooling, which protects the powder from being disturbed during the transportation, to a second press where it is further compacted under much higher loads. The compacts thus formed can be further processed to form thin, curved, densified, permanent rare earth-cobalt magnets particularly suited for use as pole pieces in small, high-torque D.C. motors.

Abstract: In a preferred embodiment thin curved rare earth-cobalt magnets supported on the interior surface of a steel casing are formed by hot isostatic compaction. Rare earth-cobalt powder is magnetically aligned and compacted to at least 65% of the theoretical density. The relatively strong, curved green compacts are positioned on a curved mandrel and placed in a closely fitting steel casing which is evacuated and sealed. The magnets are densified under isostatic gas pressure at elevated temperatures and bonded to the steel. The steel backing serves as an integral motor casing when such magnets are used in D.C. motors.