Development of controlled solid-state alignment for alnico permanent magnets in near-final shape

Journal Article · Mon Jan 09 00:00:00 EST 2017 · AIP Advances

DOI:https://doi.org/10.1063/1.4973843· OSTI ID:1349326

Anderson, Iver E.  ^[1]; Kassen, Aaron G.  ^[2]; White, Emma M. H. ^[1]; Palasyuk, Andriy ^[3]; Zhou, Lin ^[3]; Tang, Wei ^[3]; Kramer, Matthew J. ^[1]

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1. Ames Laboratory (USDOE), Ames, Iowa 50011, USA, Iowa State University, Ames, Iowa 50011, USA
2. Iowa State University, Ames, Iowa 50011, USA
3. Ames Laboratory (USDOE), Ames, Iowa 50011, USA

The 2011 price shock in the rare earth (RE) permanent magnet (PM) marketplace precipitated realization of extremely poor RE supply diversity and drove renewed research in RE-free permanent magnets such as “alnico.” Essentially, alnico is an Al-Ni-Co-Fe alloy with high magnetic saturation and T_C, but low coercivity. It also was last researched extensively in the 1970’s. Currently alnico “9” magnets with the highest energy product (10MGOe) are manufactured by directional solidification to make highly aligned anisotropic magnets. This work developed novel powder processing techniques to improve on unaligned anisotropic alnico “8H” with elevated coercivity. Gas atomization was used to produce pre-alloyed powder for binder-assisted compression molding of near-final shape magnets that were vacuum sintered to full density (<1% porosity). Biased grain growth with resulting grain alignment was achieved during a second solution annealing step, during which a uni-axial stress was applied along the axis parallel to the magnetization direction. Lastly, evaluation of heavily stressed samples (>250g) showed reduced overall loop squareness compared to unaligned (equiaxed) 8H due to grain rotation-induced misalignment, while low stresses improved squareness and greatly improved alignment compared to equiaxed magnets, with squareness approaching 0.30 and remanence ratio as high as 0.79.

• Research Organization: Ames Lab., Ames, IA (United States)
• Sponsoring Organization: USDOE Office of Energy Efficiency and Renewable Energy (EERE), Vehicle Technologies Office (EE-3V); USDOE Office of Energy Efficiency and Renewable Energy (EERE), Office of Sustainable Transportation. Vehicle Technologies Office (VTO)
• Grant/Contract Number: AC02-07CH11358
• OSTI ID: 1349326
• Alternate ID(s): OSTI ID: 1373367; OSTI ID: 1421273
• Report Number(s): IS-J-9387; AAIDBI; 10.1063/1.4973843
• Journal Information: AIP Advances, Journal Name: AIP Advances Vol. 7 Journal Issue: 5; ISSN 2158-3226
• Publisher: American Institute of Physics
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
Permanent magnets
Magnets
Coercive force
Rare earth magnets
Remanence