Method for forming samarium-iron-nitride magnet alloys
AssigneeGeneral Motors Corporation
InventorsFrederick E. Pinkerton, Carlton D. Fuerst
Life of this patent
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Abstract
In a preferred method, a molten alloy of samarium and iron is formed with a proportion of about 1:4 to about 1:9 of samarium to iron. The molten alloy is then quenched in a non-oxidizing environment at a rate sufficient to form a solid crystalline alloy in the form of a thin ribbon. The ribbon is comminuted to form a powder and the powder is nitrided in a gaseous nitrogen atmosphere. Nitriding causes nitrogen to penetrate and occupy interstitial sites in the Sm-Fe alloy, producing a magnetically hard powder with a high coercivity typically 10 kOe, usually greater than 15 kOe and as high as about 20 to about 23 kOe.
Claims12
A method of making an alloy having a nitrified Sm.sub.2 Fe.sub.17 structure, consisting of nitrogen (N), samarium (Sm) and iron (Fe), by the steps of:
- a) forming a molten alloy consisting of samarium (Sm) and iron (Fe) in an atomic ratio of about 1:4 to about 1:9 (Sm:Fe) in a non-oxidizing environment;
- b) quenching the molten alloy in a non-oxidizing environment at a rate sufficient to form an alloy ribbon having a thickness less than about 200 microns, a crystalline microstructure and a grain size less than about 500 nanometers;
- c) comminuting the alloy ribbon to a maximum cross-dimension thereof less than about 45 microns;
- and
- d) nitrifying the comminuted alloy ribbons in a non-oxidizing, nitrogen-containing atmosphere for a time and at a temperature sufficient to cause nitrogen to penetrate and occupy interstitial sites in the solid crystalline microstructure, and to provide the nitrified Sm.sub.2 Fe.sub.17 structure consisting of N, Sm and Fe and characterized by an intrinsic coercivity of at least about 10,000 Oersteds at room temperature.
A method of making an alloy having a nitrified Sm.sub.2 Fe.sub.17 structure consisting of nitrogen (N), samarium (Sm) and iron (Fe), by the steps of:
- a) forming a molten alloy consisting of samarium (Sm) and iron (Fe) in an atomic ratio of about 1:4 to about 1:9 (Sm:Fe) in a non-oxidizing environment;
- b) quenching the molten alloy in a non-oxidizing environment at a rate sufficient to form an alloy ribbon of an amorphous material or a crystalline material having a grain size less than about 500 nanometers, the ribbon having a thickness of less than about 200 microns;
- c) comminuting the alloy ribbon to a maximum cross-dimension thereof less than about 25 microns;
- d) heating the alloy ribbon in a non-oxidizing environment for a time and at a temperature sufficient to anneal the ribbon and/or to produce a crystalline microstructure and a grain size less than about 500 nanometers;
- and then
- e) nitrifying the alloy ribbon in a non-oxidizing, nitrogen-containing atmosphere for a time and at a temperature sufficient to cause nitrogen to penetrate and occupy interstitial sites in the solid crystalline microstructure, and to provide the nitrified Sm.sub.2 Fe.sub.17 structure consisting of N, Sm and Fe and characterized by an intrinsic coercivity of at least about 20,000 Oersteds at room temperature.
Dependencies are inferred from the claim text.