Grain boundary diffusion process for rare-earth magnets

Patent metadata

Field	Value
Publication number	US-10290407-B2
Application number	US-201715698102-A
Country	US
Kind code	B2
Filing date	Sep 7, 2017
Priority date	Oct 9, 2013
Publication date	May 14, 2019
Grant date	May 14, 2019

Abstract

In at least one embodiment, a single sintered magnet is provided having a concentration profile of heavy rare-earth (HRE) elements within a continuously sintered rare-earth (RE) magnet bulk. The concentration profile may include at least one local maximum of HRE element concentration within the bulk such that a coercivity profile of the magnet has at least one local maximum within the bulk. The magnet may be formed by introducing alternating layers of an HRE containing material and a magnetic powder into a mold, pressing the layers into a green compact, and sintering the green compact to form a single, unitary magnet.

First claim

What is claimed is:

1. A method of forming a rare-earth magnet comprising:
introducing alternating layers of a material including a heavy rare-earth (HRE) element or alloy and a magnetic powder including a rare-earth element or alloy into a mold;
compacting the layers into a green compact; and
sintering the green compact to form a rare-earth magnet having a concentration profile of HRE elements diffused into a rare-earth element bulk, wherein the concentration profile and a corresponding coercivity profile are substantially sinusoidal in shape along an entire thickness of the magnet.

2. The method of claim 1 , wherein at least three layers of material including a HRE element or alloy are introduced into the mold.

3. The method of claim 1 , wherein the layers of material including a HRE element or alloy have a thickness of 25 to 250 μm.

4. The method of claim 1 , wherein the layers of material including a HRE element or alloy each have a same thickness.

5. The method of claim 1 , wherein the material including a HRE element or alloy is a liquid.

6. The method of claim 1 , wherein the material including a HRE element or alloy is a powder.

7. The method of claim 6 , wherein the powder is selected from one of DyF 3 , TbF 3 , Dy 2 O 3 , Tb 2 O 3 , and DyFe.

8. The method of claim 1 , wherein the material including a HRE element or alloy is mixed with an electrically insulating material prior to being introduced into the mold.

9. The method of claim 8 , wherein the electrically insulating material includes a magnetic material.

10. A method of forming a magnet comprising:
pressing a layered assembly of rare-earth magnetic powder and heavy rare-earth elements into a green compact; and
via sintering, forming a single sintered magnet having a concentration profile of heavy rare-earth elements across an entire width of the magnet within a continuously sintered rare-earth magnet bulk, wherein the concentration profile and a corresponding coercivity profile are substantially sinusoidal in shape along an entire thickness of the magnet.

11. The method of claim 10 , wherein the green compact is pressed to a density of about 40 to 80%.

12. The method of claim 10 , further comprising applying a magnetic field to impart magnetic orientation to the magnet during the pressing step.

13. The method of claim 10 , wherein individual layers of the layered assembly are substantially evenly spaced and have substantially the same thickness.

14. The method of claim 10 , further comprising diffusing the HRE elements into grain boundaries and outer shell of the grains during the sintering step.

15. A method of forming a magnet comprising:
layering at least one of each rare-earth (RE) magnetic powder, heavy rare-earth (HRE) elements, and an electrically insulating material in a mold to form a layered assembly,
applying pressure to the layered assembly to form a green compact; and
continuously sintering the green compact into a magnet having a concentration profile of HRE elements across an entire width of the magnet within an RE magnet bulk, the electrically insulating material disposed within the magnet bulk, wherein the concentration profile and a corresponding coercivity profile across the entire width of the magnet are substantially sinusoidal in shape along an entire thickness of the magnet.

16. The method of claim 15 , wherein the continuous sintering step comprises sintering each layer to an adjacent layer.

17. The method of claim 15 , wherein individual layers of the layered assembly are substantially evenly spaced and have substantially the same thickness.

18. The method of claim 15 , wherein the electrically insulating material includes a magnetic material.

19. The method of claim 15 , further comprising diffusing the HRE elements into grain boundaries and outer shell of the grains during the sintering step.

20. The method of claim 15 , wherein a first layer and a last layer of the magnet comprise a HRE element.

Assignees

• Ford Global Tech Llc

Inventors

• Liang Feng
• Rong C Bing
• Degner Michael W

Classifications

• B22F7/06

  of composite workpieces or articles from parts, e.g. to form tipped tools {(B22F7/002 takes precedence)} · CPC title

• B22F2998/10

  Processes characterised by the sequence of their steps · CPC title

• H01F41/0293

  diffusion of rare earth elements, e.g. Tb, Dy or Ho, into permanent magnets · CPC title

• B22F2304/10

  Micron size particles, i.e. above 1 micrometer up to 500 micrometer · CPC title

• B22F2207/01

  Composition gradients · CPC title