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Title: Correlative Energy-Dispersive X-Ray Spectroscopic Tomography and Atom Probe Tomography of the Phase Separation in an Alnico 8 Alloy

Abstract

Abstract Alnico alloys have long been used as strong permanent magnets because of their ferromagnetism and high coercivity. Understanding their structural details allows for better prediction of the resulting magnetic properties. However, quantitative three-dimensional characterization of the phase separation in these alloys is still challenged by the spatial quantification of nanoscale phases. Herein, we apply a dual tomography approach, where correlative scanning transmission electron microscopy (STEM) energy-dispersive X-ray spectroscopic (EDS) tomography and atom probe tomography (APT) are used to investigate the initial phase separation process of an alnico 8 alloy upon non-magnetic annealing. STEM-EDS tomography provides information on the morphology and volume fractions of Fe–Co-rich and Νi–Al-rich phases after spinodal decomposition in addition to quantitative information of the composition of a nanoscale volume. Subsequent analysis of a portion of the same specimen by APT offers quantitative chemical information of each phase at the sub-nanometer scale. Furthermore, APT reveals small, 2–4 nm Fe-richα 1phases that are nucleated in the Ni-richα 2matrix. From this information, we show that phase separation of the alnico 8 alloy consists of both spinodal decomposition and nucleation and growth processes. The complementary benefits and challenges associated with correlative STEM-EDS and APT are discussed.

Authors:
 [1];  [1];  [2];  [2];  [2];  [1];  [1]
  1. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
  2. Ames Lab., Ames, IA (United States)
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Ames Laboratory (AMES), Ames, IA (United States)
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
1394424
Alternate Identifier(s):
OSTI ID: 1342944
Report Number(s):
IS-J-9002
Journal ID: ISSN 1431-9276; applab
Grant/Contract Number:  
AC05-00OR22725; AC02-07CH11358
Resource Type:
Accepted Manuscript
Journal Name:
Microscopy and Microanalysis
Additional Journal Information:
Journal Volume: 22; Journal Issue: 06; Journal ID: ISSN 1431-9276
Publisher:
Microscopy Society of America (MSA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; phase separation; atom probe tomography (APT); electron tomography; correlative tomography; alnico alloy

Citation Formats

Guo, Wei, Sneed, Brian T., Zhou, Lin, Tang, Wei, Kramer, Matthew J., Cullen, David A., and Poplawsky, Jonathan D. Correlative Energy-Dispersive X-Ray Spectroscopic Tomography and Atom Probe Tomography of the Phase Separation in an Alnico 8 Alloy. United States: N. p., 2016. Web. doi:10.1017/S1431927616012496.
Guo, Wei, Sneed, Brian T., Zhou, Lin, Tang, Wei, Kramer, Matthew J., Cullen, David A., & Poplawsky, Jonathan D. Correlative Energy-Dispersive X-Ray Spectroscopic Tomography and Atom Probe Tomography of the Phase Separation in an Alnico 8 Alloy. United States. doi:10.1017/S1431927616012496.
Guo, Wei, Sneed, Brian T., Zhou, Lin, Tang, Wei, Kramer, Matthew J., Cullen, David A., and Poplawsky, Jonathan D. Wed . "Correlative Energy-Dispersive X-Ray Spectroscopic Tomography and Atom Probe Tomography of the Phase Separation in an Alnico 8 Alloy". United States. doi:10.1017/S1431927616012496. https://www.osti.gov/servlets/purl/1394424.
@article{osti_1394424,
title = {Correlative Energy-Dispersive X-Ray Spectroscopic Tomography and Atom Probe Tomography of the Phase Separation in an Alnico 8 Alloy},
author = {Guo, Wei and Sneed, Brian T. and Zhou, Lin and Tang, Wei and Kramer, Matthew J. and Cullen, David A. and Poplawsky, Jonathan D.},
abstractNote = {Abstract Alnico alloys have long been used as strong permanent magnets because of their ferromagnetism and high coercivity. Understanding their structural details allows for better prediction of the resulting magnetic properties. However, quantitative three-dimensional characterization of the phase separation in these alloys is still challenged by the spatial quantification of nanoscale phases. Herein, we apply a dual tomography approach, where correlative scanning transmission electron microscopy (STEM) energy-dispersive X-ray spectroscopic (EDS) tomography and atom probe tomography (APT) are used to investigate the initial phase separation process of an alnico 8 alloy upon non-magnetic annealing. STEM-EDS tomography provides information on the morphology and volume fractions of Fe–Co-rich and Νi–Al-rich phases after spinodal decomposition in addition to quantitative information of the composition of a nanoscale volume. Subsequent analysis of a portion of the same specimen by APT offers quantitative chemical information of each phase at the sub-nanometer scale. Furthermore, APT reveals small, 2–4 nm Fe-richα1phases that are nucleated in the Ni-richα2matrix. From this information, we show that phase separation of the alnico 8 alloy consists of both spinodal decomposition and nucleation and growth processes. The complementary benefits and challenges associated with correlative STEM-EDS and APT are discussed.},
doi = {10.1017/S1431927616012496},
journal = {Microscopy and Microanalysis},
number = 06,
volume = 22,
place = {United States},
year = {2016},
month = {12}
}

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Figures / Tables:

Figure-1 Figure-1: Schematic experimental workflow for conducting correlative STEM-EDS and APT tomography. (a) Electropolishing adapter and set up; (b) The ideal geometry of the rod-shaped holder and the SEM/FIB adapter that is suitable for dual SEM/FIB imaging; (c) Lift out process of a (100) targeted grain. (d) Final tip shape aftermore » sample preparation; (e) The Fischione tomography holder containing the needle shaped specimen; (f) APT puck holder dedicated for rod specimens.« less

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