Preparation of mnbi ltp magnet by direct sintering

Patent metadata

Field	Value
Publication number	US-2018366247-A1
Application number	US-201715627517-A
Country	US
Kind code	A1
Filing date	Jun 20, 2017
Priority date	Jun 20, 2017
Publication date	Dec 20, 2018
Grant date	—

Abstract

A method comprising sintering a Mn and Bi powder compact at a first temperature for a first predetermined duration, based on the first temperature, and sintering the compact at a second temperature, less than the first temperature, for a second predetermined duration, greater than the first duration, is disclosed. The sintering at a first temperature for a first predetermined duration generates a predetermined MnBi LTP transition driving force to decrease a formation energy barrier for transition to MnBi LTP. Sintering the compact at the second temperature for the second predetermined duration forms a magnet containing the MnBi LTP.

First claim

What is claimed is:

1 . A method comprising:
sintering a Mn and Bi powder compact at a first temperature for a first predetermined duration, based on the first temperature, to generate a predetermined MnBi LTP transition driving force to decrease a formation energy barrier for transition to MnBi LTP; and sintering the compact at a second temperature, less than the first temperature, for a second predetermined duration, greater than the first duration, to form a magnet containing the MnBi LTP.

2 . The method of claim 1 , wherein the first predetermined duration is between about 1 and 120 minutes.

3 . The method of claim 2 , wherein the first temperature is between about 360 and 900° C.

4 . The method of claim 1 , wherein the second predetermined duration is between about 1 and 48 hours.

5 . The method of claim 4 , wherein the second temperature is about 260 to 450° C.

6 . The method of claim 1 , further comprising mixing and pressing the Mn and Bi powder to form the compact.

7 . The method of claim 1 , wherein an x-ray diffraction peak intensity of the MnBi LTP is at least twice that of a Bi peak in the magnet.

8 . The method of claim 1 , further comprising crushing and milling the magnet to form an MnBi LTP containing powder, pressing the MnBi LTP containing powder into a LTP containing compact, and repeating the sinterings.

9 . The method of claim 1 , further comprising crushing and milling the magnet to form an MnBi LTP containing powder, pressing the MnBi LTP containing powder into a LTP containing compact, and repeating the sintering at the second temperature for the second predetermined duration.

10 . A high yield MnBi LTP magnet formed by the method of claim 1 .

11 . A method of producing a high yield MnBi LTP magnet comprising:
sintering a Mn and Bi powder compact at a first temperature for a first duration to provide a phase transition driving force for nucleation and growth of MnBi LTP; and sintering at a second temperature, less than the first duration, for a second duration, greater than the first duration, such that an MnBi LTP x-ray peak intensity is at least twice that of Bi.

12 . The method of claim 11 , further comprising crushing and milling the compact to form an MnBi LTP containing powder.

13 . The method of claim 12 , further comprising pressing the MnBi LTP containing powder into an LTP containing compact, and repeating both the sinterings, or the sintering at the second temperature for the second duration.

14 . The method of claim 12 , wherein the milling includes low energy ball milling, cryo-milling, or jet milling.

15 . The method of claim 11 , wherein the first temperature is between about 360 and 900° C.

16 . The method of claim 15 , wherein the first duration is between about 1 and 120 minutes.

17 . The method of claim 11 , wherein the second temperature is about 260 to 450° C.

18 . The method of claim 17 , wherein the second duration is between about 1 and 48 hours.

19 . The method of claim 11 , wherein the Mn and Bi powder compact is about a 0.8:1 to 1:0.8 atomic ratio mix of milled Mn powder and milled Bi powder.

20 . The method of claim 11 , wherein the first temperature is about 660° C. and the first duration is between about 40 and 80 minutes, and the second temperature is about 340° C. and the second duration is about 24 hours.

Assignees

• Ford Global Tech Llc

Inventors

• Li Wanfeng

Classifications

• C22C1/04

  by powder metallurgy (C22C1/08 takes precedence) · CPC title

• C22C1/047

  comprising intermetallic compounds {(C22C1/0441 takes precedence)} · CPC title

• B22F2009/043

  by ball milling · CPC title

• C22C2202/02

  Magnetic · CPC title

• B22F3/162

  Machining, working after consolidation · CPC title