Bulk anisotropic exchange-spring magnets and method of producing the same

Patent metadata

Field	Value
Publication number	US-11145445-B2
Application number	US-201715791875-A
Country	US
Kind code	B2
Filing date	Oct 24, 2017
Priority date	Dec 14, 2016
Publication date	Oct 12, 2021
Grant date	Oct 12, 2021

Abstract

A method of preparing a permanent magnet nanocomposite. The method includes melting a precursor alloy having a hard magnetic phase and a magnetically soft phase. The hard magnetic phase has less than a stoichiometric amount of rare earth metal or noble metal. The melted precursor is cast into flakes and milled into a powder. The powder may then be pressure crystalized.

First claim

What is claimed is:

1. A method of preparing an anisotropic permanent magnet nanocomposite, the method comprising:
melting a precursor alloy having a hard magnetic phase and a magnetically soft phase, the hard magnetic phase comprising less than a stoichiometric amount of a rare earth metal or a noble metal;
casting the melted precursor alloy into flakes;
milling the casted flakes into a powder; and
pressure crystalizing the powder by:
pressurizing and heating the powder at a crystallization pressure ranging from about 0.5 GPa to about 3 GPa and at a crystallization temperature over a pressurizing time, wherein the powder is pressurized at a rate of about 200 MPa/min;
holding the powder at the crystallization temperature and the crystallization pressure over a hold time to promote crystal growth; and
rapidly quenching the crystal growth to a temperature less than about 200° C. in less than about a minute.

2. The method of claim 1 , wherein the hard magnetic phase comprises:
Nd—Fe—B, Sm—Co, Sm—Fe—N, Fe—Pt, or Co—Pt.

3. The method of claim 2 , wherein the permanent magnet nanocomposite is SmCo 5 , the rare earth metal is Sm, and the stoichiometric amount is about 16.6 at. %.

4. The method of claim 2 , wherein the permanent magnet nanocomposite is Sm 2 Co 17 , the rare earth metal is Sm, and the stoichiometric amount is about 10.5 at. %.

5. The method of claim 2 , wherein the permanent magnet nanocomposite is Sm 2 Fe 17 N 3 , the rare earth metal is Sm, and the stoichiometric amount is about 9.1 at. %.

6. The method of claim 2 , wherein the permanent magnet nanocomposite is FePt or CoPt, the noble metal is Pt or Co, and the stoichiometric amount is about 50 at. %.

7. The method of claim 2 , wherein the permanent magnet nanocomposite is Pr 2 Fe 14 B, the rare earth metal is Pr, and the stoichiometric amount is about 11.76 at. %.

8. The method of claim 2 , wherein the permanent magnet nanocomposite is Pr 2 Co 5 , the rare earth metal is Pr, and the stoichiometric amount is about 16.6 at. %.

9. The method of claim 2 , wherein the permanent magnet nanocomposite is Nd 2 Fe 14 B, the rare earth metal is Nd, and the stoichiometric amount is about 11.76 at. %.

10. The method of claim 1 , wherein the magnetically soft phase comprises:
α-Fe, Fe—Co, Fe—N, Co, Ni, or combinations thereof.

11. The method of claim 1 , wherein melting the precursor alloy further comprises:
arc melting, induction melting, levitation melting, or powder metallurgy processing.

12. The method of claim 1 , wherein casting the melted precursor alloy further comprises:
melt spinning, splat quenching, or planar flow casting.

13. The method of claim 1 , wherein the flakes yielded from casting the melted precursor alloy are amorphous or crystalline.

14. The method of claim 13 , wherein milling the casted flakes further comprises cryomilling.

15. The method of claim 1 , wherein heating the powder occurs at a rate of about 100 K/min.

16. The method of claim 1 , wherein the pressurizing time is less than 5 min.

17. The method of claim 1 , wherein the pressurizing time is less than 3 min.

18. The method of claim 1 , wherein the hold time is less than 20 min.

19. The method of claim 1 , wherein rapidly quenching includes using a gas quench.

20. The method of claim 1 , wherein pressurizing and crystalizing the powder comprises inductively heating or resistively heating.

21. The method of claim 1 , wherein pressurizing and crystalizing are configured to initiate nucleation.

Assignees

• Us Gov Air Force
• Us Air Force

Inventors

• Turgut Zafer

Classifications

• C22C38/005 Primary

  containing rare earths, i.e. Sc, Y, Lanthanides · CPC title

• H01F1/0579

  with exchange spin coupling between hard and soft nanophases, e.g. nanocomposite spring magnets · CPC title

• C22C33/0278

  with at least one alloying element having a minimum content above 5% · CPC title

• C22C38/002

  containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60 · CPC title

• C22C38/00

  Ferrous alloys, e.g. steel alloys (cast-iron alloys C22C37/00) · CPC title