Heat Treatable Magnets Having Improved Alignment Through Application Of External Magnetic Field During Binder-Assisted Molding
Improved manufacturing processes and resulting anisotropic permanent magnets, such as for example alnico permanent magnets, having highly controlled and aligned microstructure in the solid state are provided. A certain process embodiment involves applying a particular orientation and strength of magnetic field to loose, binder-coated magnet alloy powder particles in a compact-forming device as they are being formed into a compact in order to preferentially align the magnet alloy powder particles in the compact. The preferential alignment of the magnet alloy powder particle is locked in place in the compact by the binder after compact forming is complete. After removal from the device, the compact can be subjected to a subsequent sintering or other heat treating operation.
1 .- 19 . (canceled)
20 . An anisotropic permanent magnet compact, comprising permanent magnet alloy particles consolidated in the presence of a binder and in the presence of a magnetic field that imparts a preferential alignment to the particles that is locked in place in the compact by the binder.
21 . The compact of claim 20 wherein the alloy particles comprise polycrystalline particles.
22 . The compact of claim 20 wherein all of the alloy particles have a diameter less than 20 microns.
23 . The compact of claim 20 wherein the alloy particles comprise AlNiCo powder.
24 . The compact of claim 20 wherein the alloy particles comprise binder-coated particles.
25 . The compact of claim 24 wherein the binder-coated particles have a polymer binder coating on the particles.
26 . The compact of claim 20 wherein the particles include an oxide coating on the individual particles beneath a particle binder coating.
27 . The compact of claim 20 wherein the alloy particles comprise, in weight. %, about 7 to about 8% Al, about 13 to about 15% Ni, about 24 to about 42% Co, up to about 3% Cu, up to about 8% Ti, and balance Fe and incidental impurities.
28 . The method of claim 27 wherein the alloy particles comprises, in weight.%, 7.1% Al, 13.0% Ni, 40.1% Co, up to 3.0% Cu, up to 6.5% Ti, up to 0.5% Nb, and balance substantially Fe and incidental impurities.
29 . An anisotropic permanent magnet comprising the compact of claim 20 that has been heat treated to achieve grain growth in a direction of the preferential alignment within at least a portion of the volume of compact.
30 . The magnet of claim 29 which has been thermally debinded and sintered in a single phase high temperature region of the magnet alloy for a time to produce grain growth
31 . The magnet of claim 30 that has a single crystal microstructure or a microstructure having enlarged grains having a millimeter-sized grain dimension in a grain growth direction.