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

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.
ORCiD logo [1] ; ORCiD logo [2] ;  [1] ;  [3] ;  [3] ;  [3] ;  [1]
  1. Ames Lab. and Iowa State Univ., Ames, IA (United States)
  2. Iowa State Univ., Ames, IA (United States)
  3. Ames Lab., Ames, IA (United States)
Publication Date:
Report Number(s):
Journal ID: ISSN 2158-3226; AAIDBI
Grant/Contract Number:
Published Article
Journal Name:
AIP Advances
Additional Journal Information:
Journal Volume: 7; Journal Issue: 5; Journal ID: ISSN 2158-3226
American Institute of Physics (AIP)
Research Org:
Ames Laboratory (AMES), Ames, IA (United States)
Sponsoring Org:
USDOE Office of Energy Efficiency and Renewable Energy (EERE), Vehicle Technologies Office (EE-3V)
Country of Publication:
United States
36 MATERIALS SCIENCE; Permanent magnets; Magnets; Coercive force; Rare earth magnets; Remanence
OSTI Identifier:
Alternate Identifier(s):
OSTI ID: 1373367; OSTI ID: 1421273