Nanostructured Mn-Al permanent magnets and methods of producing same

• US 8,999,233 B2
• Filed: 12/16/2011
• Issued: 04/07/2015
• Est. Priority Date: 10/27/2005
• Status: Active Grant

• Current Assignee: The Trustees of Dartmounth College (Dartmouth College)
• Original Assignee: The Trustees of Dartmounth College (Dartmouth College)
• Inventors: Baker, Ian
• Primary Examiner(s): LEE, REBECCA Y
• Application Number:
  US13/328,903
• Publication Number:
  US 20120090740A1
• Time in Patent Office: 1,208 Days
• Field of Search: 148/314, 148/559, 420/591
• US Class Current: 420/591
• CPC Class Codes: C22C 22/00 Alloys based on manganese
• CPC Class Codes: C22F 1/16 of other metals or alloys based thereon
• CPC Class Codes: H01F 1/047 Alloys characterised by their composition
• CPC Class Codes: H01F 1/0579 with exchange spin coupling between hard and soft nanophases, e.g. nanocomposite spring magnets
• CPC Class Codes: H01F 1/058 and IVa elements, e.g. Gd2Fe14C
• CPC Class Codes: H01F 1/068 having a L10 crystallographic structure, e.g. [Co,Fe][Pt,Pd] (nano)particles
• CPC Class Codes: H01F 1/083 in a bonding agent
• CPC Class Codes: H01F 41/0266 Moulding; Pressing H01F41/0273 takes precedence; hard magnetic particles H01F1/06, H01F1/11

Abstract

Nanostructured Mn—Al, Mn—Al—C permanent magnets are disclosed. The magnets have high coercivities (about 4.8 kOe and 5.2 kOe) and high magnetization values. An intennetallic composition includes a ternary transition metal modified manganese aluminum alloy Mn—Al—Fe, Mn—Al—Ni, or Mn—Al—Co having at least about 80% of a magnetic τ phase and permanent magnetic properties. The alloy may have a saturation magnetization value of at least 96 emu/g with approximately 5% ternary transition metal replacing Al. The alloy may also have a saturation magnetization value of at least 105 emu/g with 10% ternary transition metal replacing Al.

Claims

1. An intermetallic composition comprising a ternary transition metal modified manganese aluminum alloy comprising a bulk nanostructured alloy with at least about 80% of a magnetic τ

phase and having permanent magnetic properties,

the bulk alloy having a macroscopic composition of Mn_XAl_YT_Z, wherein

T is a ternary transition metal selected from a group consisting of iron, cobalt and nickel,

X ranges from 50 atomic % to 60 atomic %,

X +Y +Z =100 atomic %, and

Z is an amount less than 10 atomic % sufficient to impart a saturation magnetization of at least 96 emu/g and the τ

phase comprises Mn, Al and a ternary transition metal selected from the group consisting of iron, cobalt and nickel.

2. The intermetallic composition of claim 1, wherein Y ranges from 36-46 atomic %.

3. The intermetallic composition of claim 1, wherein the alloy comprises approximately 54 atomic % manganese, approximately 41 atomic % aluminum, and approximately 5 atomic % ternary transition metal.

4. The intermetallic composition of claim 1, wherein the alloy comprises approximately 54 atomic % manganese, approximately 36 atomic % aluminum, and approximately 10 atomic % ternary transition metal.

5. The intermetallic composition of claim 4, wherein the permanent magnetic properties comprise a saturation magnetization value of at least 105 emu/g.

6. The intermetallic composition of claim 1 wherein the bulk nanostructured alloy further includes γ

and β

phases.