Method for preparation of severely plastically deformed particulates for manganese-aluminum-based alloy permanent magnets

Patent metadata

Field	Value
Publication number	US-2026081068-A1
Application number	US-202418818930-A
Country	US
Kind code	A1
Filing date	Aug 29, 2024
Priority date	Sep 1, 2023
Publication date	Mar 19, 2026
Grant date	—

Abstract

A method of manufacturing permanent magnet materials for use in making MnAl-based alloy permanent magnets includes providing an ε-phase MnAl-based alloy solid feedstock, end-milling the ε-phase MnAl-based alloy solid feedstock to produce a plurality of severely plastically deformed ε-phase MnAl-based alloy particulates, and creating the permanent magnet materials by thermally processing the plurality of ε-phase MnAl-based alloy particulates to produce a plurality of τ-phase MnAl-based alloy particulates. In addition, the method may further include making a permanent magnet by mixing the τ-phase MnAl-based alloy particulates with a binder to produce a mixture, and forming the mixture into a desired shaped for the permanent magnet. The forming step may include one or more of injection molding the mixture, compression bonding the mixture, calendering the mixture or extruding the mixture.

First claim

What is claimed is:

1 . A method of manufacturing permanent magnet materials for use in making MnAl-based alloy permanent magnets, comprising:
providing an ε-phase MnAl-based alloy solid feedstock; end-milling the ε-phase MnAl-based alloy solid feedstock to produce a plurality of severely plastically deformed ε-phase MnAl-based alloy particulates; and creating the permanent magnet materials by thermally processing the plurality of ε-phase MnAl-based alloy particulates to produce a plurality of τ-phase MnAl-based alloy particulates.

2 . The method according to claim 1 , wherein the plurality of ε-phase MnAl-based alloy particulates have a refined microstructure having a sub-micron (<1 μm) to nanometer scale (≤100 nm) grain size.

3 . The method according to claim 2 , wherein the microstructure comprises a self-similar morphology.

4 . The method according to claim 1 , wherein the ε-phase MnAl-based alloy solid feedstock is a binary ε-phase MnAl alloy solid feedstock, wherein the ε-phase MnAl-based alloy particulates are ε-phase MnAl alloy particulates, and wherein the τ-phase MnAl-based alloy particulates are τ-phase MnAl alloy particulates.

5 . The method according to claim 1 , wherein the ε-phase MnAl-based alloy solid feedstock is a micro-alloyed ε-phase MnAl—X alloy solid feedstock, where X represents one or more micro-alloying elements, wherein the ε-phase MnAl-based alloy particulates are micro-alloyed ε-phase MnAl-X alloy particulates, and wherein the τ-phase MnAl-based alloy particulates are micro-alloyed τ-phase MnAl—X alloy particulates.

6 . The method according to claim 5 , where X represents one or more micro-alloying elements at concentrations smaller than 3 atomic (molar) percent.

7 . The method according to claim 1 , wherein the end milling is performed at room temperature.

8 . The method according to claim 1 , wherein the ε-phase MnAl-based alloy solid feedstock has a composition of 54 at. % Mn and 46 at. % Al.

9 . The method according to claim 1 , wherein the thermally processing comprises thermal annealing.

10 . The method according to claim 9 , wherein the thermal annealing comprises isothermal annealing at temperatures ranging from 673 K to 723 K.

11 . The method according to claim 9 , wherein the thermal annealing is performed under vacuum.

12 . The method according to claim 11 , wherein the thermal annealing is performed under vacuum with a 10 K/s heating rate and subsequent isothermal annealing holds at 623 K, 673 K, 698 K, and 723 K.

13 . The method according to claim 9 , wherein the end milling is performed with a tool speed of 4200 RPM and wherein the thermal annealing comprises annealing for 20 min at 673K.

14 . The method according to claim 1 , wherein the end milling is performed with stage speeds ranging from 1 mm/s to 13 mm/s, radial depths of cut, r c , ranging from 0.05 mm to 0.5 mm, axial depths of cut, a c , ranging from 0.1 mm to 0.2 mm, and spindle/tool rotational speeds in the range of 100 rotations per minute (RPM) to 3000 RPM for manual end-milling and 750 RPM to 4200 RPM for CNC end-milling.

15 . The method according to claim 14 , wherein the stage speeds are ≥10 mm/s, the rotational spindle/tool speeds are ≥600 RPM, and the radial depth of cut, rc is ≤0.1 mm.

16 . The method according to claim 14 , wherein the end milling is performed with a rotational tool speed of 3000 RPM using a 13 mm/s stage speed and constant radial depths of cut of 0.05 mm and constant axial depths of cut of 0.1 mm.

17 . The method according to claim 1 , wherein the end milling is performed with a fluted chamfer end mill cutting tool.

18 . The method according to claim 1 , wherein the end milling is performed with a flute fine tooth roughing end mill cutting tool.

19 . The method according to claim 1 , wherein the ε-phase MnAl-based alloy particulates have a saw-tooth-like appearance at a free surface thereof not in contact with a cutting tool used in the end-milling.

20 . The method according to claim 1 , wherein the providing the ε-phase MnAl-based alloy solid feedstock comprises vacuum induction melting of elemental metal Mn and Al followed by casting into a number of cylindrical rods with a target composition of Mn 54 Al 46 .

21 . The method according to claim 20 , wherein the providing the ε-phase MnAl-based alloy solid feedstock further comprises sectioning the rods into a number of sectioned pieces and solutionizing the number of sectioned pieces to produce the ε-phase MnAl alloy solid feedstock.

22 . The method according to claim 21 , wherein the solutionizing comprises heat treating the sectioned pieces.

23 . The method according to claim 22 , wherein the solutionizing comprises heat treating the sectioned pieces under an argon atmosphere.

24 . The method according to claim 22 , wherein the solutionizing comprises heat treating the sectioned pieces at 1323 K (1050° C.).

25 . The method according to claim 24 , wherein the solutionizing comprises heat treating the sectioned pieces at 1323 K (1050° C.) for 2 hours.

26 . The method according to claim 22 , wherein the solutionizing comprises heat treating the sectioned pieces followed by water quenching.

27 . The method according to claim 19 , wherein the vacuum induction melting of elemental metal Mn and Al is done with a purity of 99.95%.

28 . The method according to claim 1 , wherein the end-milling the ε-phase MnAl-based alloy solid feedstock to produce the plurality of severely plastically deformed ε-phase MnAl-based alloy particulates is done in a single end milling pass.

29 . A method of making a permanent magnet, comprising:
making permanent magnet materials according to claim 1 including the τ-phase MnAl-based alloy particulates; mixing the τ-phase MnAl-based alloy particulates with a binder to produce a mixture; and forming the mixture into a desired shaped for the permanent magnet.

30 . The method according to claim 29 , wherein the forming includes one or more of injection molding the mixture, compression bonding the mixture, calendering the mixture or extruding the mixture.

Assignees

• Univ Pittsburgh Commonwealth Sys Higher Education

Inventors

• Wiezorek Jorg M
• Meenakshisundaram Ravi Shankar

Classifications

• B22F2009/001

  from scrap particles · CPC title

• C22C1/04

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

• C22C2202/02

  Magnetic · CPC title

• H01F41/0253 Primary

  for manufacturing permanent magnets · CPC title

• B22F2009/045

  by other means than ball or jet milling · CPC title