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Title: On spinodal decomposition in alnico - A transmission electron microscopy and atom probe tomography study

Here, alnico is a prime example of a finely tuned nanostructure whose magnetic properties are intimately connected to magnetic annealing (MA) during spinodal transformation and subsequent lower temperature annealing (draw) cycles. Using a combination of transmission electron microscopy and atom probe tomography, we show how these critical processing steps affect the local composition and nanostructure evolution with impact on magnetic properties. The nearly 2-fold increase of intrinsic coercivity (H ci) during the draw cycle is not adequately explained by chemical refinement of the spinodal phases. Instead, increased Fe-Co phase (α 1) isolation, development of Cu-rich spheres/rods/blades and additional α 1 rod precipitation that occurs during the MA and draw, likely play a key role in Hci enhancement. Chemical ordering of the Al-Ni-phase (α 2) and formation of Ni-rich (α 3) may also contribute. Unraveling of the subtle effect of these nano-scaled features is crucial to understanding on how to improve shape anisotropy in alnico magnets.
Authors:
 [1] ;  [2] ;  [2] ;  [1] ;  [1] ;  [1] ;  [1]
  1. Ames Lab., Ames, IA (United States)
  2. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Publication Date:
Report Number(s):
IS-J-9646
Journal ID: ISSN 1359-6454; PII: S1359645418303197
Grant/Contract Number:
AC02-07CH11358
Type:
Accepted Manuscript
Journal Name:
Acta Materialia
Additional Journal Information:
Journal Volume: 153; Journal Issue: C; Journal ID: ISSN 1359-6454
Publisher:
Elsevier
Research Org:
Ames Laboratory (AMES), Ames, IA (United States)
Sponsoring Org:
USDOE
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; Magnetic; Microstructure; Spinodal decomposition; Atom-probe tomography; TEM; STEM HAADF
OSTI Identifier:
1454574

Zhou, Lin, Guo, Wei, Poplawsky, J. D., Ke, Liqin, Tang, Wei, Anderson, I. E., and Kramer, M. J.. On spinodal decomposition in alnico - A transmission electron microscopy and atom probe tomography study. United States: N. p., Web. doi:10.1016/j.actamat.2018.04.042.
Zhou, Lin, Guo, Wei, Poplawsky, J. D., Ke, Liqin, Tang, Wei, Anderson, I. E., & Kramer, M. J.. On spinodal decomposition in alnico - A transmission electron microscopy and atom probe tomography study. United States. doi:10.1016/j.actamat.2018.04.042.
Zhou, Lin, Guo, Wei, Poplawsky, J. D., Ke, Liqin, Tang, Wei, Anderson, I. E., and Kramer, M. J.. 2018. "On spinodal decomposition in alnico - A transmission electron microscopy and atom probe tomography study". United States. doi:10.1016/j.actamat.2018.04.042.
@article{osti_1454574,
title = {On spinodal decomposition in alnico - A transmission electron microscopy and atom probe tomography study},
author = {Zhou, Lin and Guo, Wei and Poplawsky, J. D. and Ke, Liqin and Tang, Wei and Anderson, I. E. and Kramer, M. J.},
abstractNote = {Here, alnico is a prime example of a finely tuned nanostructure whose magnetic properties are intimately connected to magnetic annealing (MA) during spinodal transformation and subsequent lower temperature annealing (draw) cycles. Using a combination of transmission electron microscopy and atom probe tomography, we show how these critical processing steps affect the local composition and nanostructure evolution with impact on magnetic properties. The nearly 2-fold increase of intrinsic coercivity (Hci) during the draw cycle is not adequately explained by chemical refinement of the spinodal phases. Instead, increased Fe-Co phase (α1) isolation, development of Cu-rich spheres/rods/blades and additional α1 rod precipitation that occurs during the MA and draw, likely play a key role in Hci enhancement. Chemical ordering of the Al-Ni-phase (α2) and formation of Ni-rich (α3) may also contribute. Unraveling of the subtle effect of these nano-scaled features is crucial to understanding on how to improve shape anisotropy in alnico magnets.},
doi = {10.1016/j.actamat.2018.04.042},
journal = {Acta Materialia},
number = C,
volume = 153,
place = {United States},
year = {2018},
month = {4}
}