skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Texture development and coercivity enhancement in cast alnico 9 magnets

Authors:
 [1]; ORCiD logo [2];  [2]; ORCiD logo [2];  [1]; ORCiD logo [3];  [3];  [3];  [4];  [1]
  1. Department of Physics and Astronomy, University of Nebraska, Lincoln, NE 68588, USA, Nebraska Center for Materials and Nanoscience (NCMN), University of Nebraska, Lincoln, NE 68588, USA
  2. Nebraska Center for Materials and Nanoscience (NCMN), University of Nebraska, Lincoln, NE 68588, USA
  3. Ames Lab, Iowa State University, Ames, IA 50011, USA
  4. Nebraska Center for Materials and Nanoscience (NCMN), University of Nebraska, Lincoln, NE 68588, USA, Department of Mechanical and Materials Engineering, University of Nebraska, Lincoln, NE 68588, USA
Publication Date:
Sponsoring Org.:
USDOE
OSTI Identifier:
1414985
Grant/Contract Number:
AC02-07CH11358
Resource Type:
Journal Article: Publisher's Accepted Manuscript
Journal Name:
AIP Advances
Additional Journal Information:
Journal Volume: 8; Journal Issue: 5; Related Information: CHORUS Timestamp: 2017-12-27 12:21:03; Journal ID: ISSN 2158-3226
Publisher:
American Institute of Physics
Country of Publication:
United States
Language:
English

Citation Formats

Zhang, Wenyong, Valloppilly, Shah, Li, Xingzhong, Yue, Lanping, Skomski, Ralph, Anderson, Iver, Kramer, Matthew, Tang, Wei, Shield, Jeff, and Sellmyer, David J. Texture development and coercivity enhancement in cast alnico 9 magnets. United States: N. p., 2018. Web. doi:10.1063/1.5007171.
Zhang, Wenyong, Valloppilly, Shah, Li, Xingzhong, Yue, Lanping, Skomski, Ralph, Anderson, Iver, Kramer, Matthew, Tang, Wei, Shield, Jeff, & Sellmyer, David J. Texture development and coercivity enhancement in cast alnico 9 magnets. United States. doi:10.1063/1.5007171.
Zhang, Wenyong, Valloppilly, Shah, Li, Xingzhong, Yue, Lanping, Skomski, Ralph, Anderson, Iver, Kramer, Matthew, Tang, Wei, Shield, Jeff, and Sellmyer, David J. Tue . "Texture development and coercivity enhancement in cast alnico 9 magnets". United States. doi:10.1063/1.5007171.
@article{osti_1414985,
title = {Texture development and coercivity enhancement in cast alnico 9 magnets},
author = {Zhang, Wenyong and Valloppilly, Shah and Li, Xingzhong and Yue, Lanping and Skomski, Ralph and Anderson, Iver and Kramer, Matthew and Tang, Wei and Shield, Jeff and Sellmyer, David J.},
abstractNote = {},
doi = {10.1063/1.5007171},
journal = {AIP Advances},
number = 5,
volume = 8,
place = {United States},
year = {Tue May 01 00:00:00 EDT 2018},
month = {Tue May 01 00:00:00 EDT 2018}
}

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record at 10.1063/1.5007171

Save / Share:
  • Recently, interest in alnico magnetic alloys has been rekindled due to their potential to substitute for rare-earth based permanent magnets provided modest improvements in their coercivity can be achieved without loss of saturation magnetization. Recent experimental studies have indicated that atomic and magnetic structure of the two phases (one AlNi-based, the other FeCo-based) that comprise these spinodally decomposed alloy is not as simple as previously thought. A key issue that arises is the distribution of Fe, Co, and Ti within the AlNi-based matrix phase. In this paper, we report the results of first-principles calculations of the site preference of ternarymore » alloying additions in DO{sub 3} Fe{sub 3}Al, Co{sub 3}Al, and Ni{sub 3}Al alloys, as models for the aluminide phase. For compound compositions that are Al rich, which correspond to experimental situation, Ti and Fe are found to occupy the α sites, while Co and Ni prefer the γ sites of the DO{sub 3} lattice. An important finding is that the magnetic moments of transition metals in Fe{sub 3}Al and Co{sub 3}Al are ordered ferromagnetically, whereas the Ni{sub 3}Al were found to be nonmagnetic unless the Fe or Co is added as a ternary element.« less
  • Recently, interest in alnico magnetic alloys has been rekindled due to their potential to substitute for rare-earth based permanent magnets provided modest improvements in their coercivity can be achieved without loss of saturation magnetization. Recent experimental studies have indicated that atomic and magnetic structure of the two phases (one AlNi-based, the other FeCo-based) that comprise these spinodally decomposed alloy is not as simple as previously thought. A key issue that arises is the distribution of Fe, Co and Ti within the AlNi-based matrix phase. In our paper we report the results of first-principles calculations of the site preference of ternarymore » alloying additions in DO 3 Fe 3Al, Co 3Al and Ni 3Al alloys, as models for the aluminide phase. For compound compositions that are Al rich, which corresponds to experimental situation, Ti and Fe are found to occupy the sites, while Co and Ni prefer the sites of the DO 3 lattice. Finally, an important finding is that the magnetic moments of transition metals in Fe 3Al and Co 3Al are ordered ferromagnetically, whereas the Ni3Al were found to be nonmagnetic unless the Fe or Co are added as a ternary element.« less
  • Nd-Fe-B as-cast alloys in the form of small ingots 4--5 mm thick and with composition Nd{sub 2.1}Fe{sub 14}B were transformed into high coercivity magnets using the hydrogenation disproportionation desorption (HDD) process without decrepitation of the blocks taking place. Magnetic measurements revealed that it was possible to produce blocks with coercivity of {similar to}780 kA m{sup {minus}1}, remanence of {similar to}680 mT and a {ital BH}{sub max} of {similar to}68 kJ m{sup {minus}3} (8.6 MGOe). The high coercivities in these samples were attributed to the disproportionation and subsequent recrystallization process. SEM metallographs of the samples processed at optimum temperature revealed anmore » absence of the original large ({similar to}200 {mu}m) grains of Nd{sub 2}Fe{sub 14}B containing areas of free iron; instead an extremely fine grained, submicron, microstructure of single phase Nd{sub 2}Fe{sub 14}B grains was observed. In samples processed at temperatures higher than that found to be the optimum, larger Nd{sub 2}Fe{sub 14}B grains with extremely rectangular morphologies could be observed growing from surrounding submicron matrix grains. Domain patterns observed on these larger grains, using the Kerr effect, indicated that Nd{sub 2}Fe{sub 14}B matrix grains appear to grow predominantly with rectangular morphologies from the disproportionated material with the {ital a} and {ital c} crystal axis running parallel to the edges of the rectangle.« less
  • 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 tomore » 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.« less
    Cited by 1
  • 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 tomore » 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.« less