A combined APT and SANS investigation of α′ phase precipitation in neutron-irradiated model FeCrAl alloys

Samuel A. Briggs; Philip D. Edmondson; Kenneth C. Littrell; Yukinori Yamamoto; Richard H. Howard; Charles R. Daily; Kurt A. Terrani; Kumar Sridharan; Kevin G. Field

doi:10.1016/j.actamat.2017.02.077

A combined APT and SANS investigation of α′ phase precipitation in neutron-irradiated model FeCrAl alloys

Samuel A. Briggs, Philip D. Edmondson, Kenneth C. Littrell, Yukinori Yamamoto, Richard H. Howard, Charles R. Daily, Kurt A. Terrani, Kumar Sridharan, Kevin G. Field

Research output: Contribution to journal › Article › peer-review

145 Scopus citations

Abstract

FeCrAl alloys are currently under consideration for accident-tolerant fuel cladding applications in light water reactors owing to their superior high-temperature oxidation and corrosion resistance compared to the Zr-based alloys currently employed. However, their performance could be limited by precipitation of a Cr-rich α^′ phase that tends to embrittle high-Cr ferritic Fe-based alloys. In this study, four FeCrAl model alloys with 10–18 at.% Cr and 5.8–9.3 at.% Al were neutron-irradiated to nominal damage doses up to 7.0 displacements per atom at a target temperature of 320 °C. Small angle neutron scattering techniques were coupled with atom probe tomography to assess the composition and morphology of the resulting α^′ precipitates. It was demonstrated that Al additions partially destabilize the α^′ phase, generally resulting in precipitates with lower Cr contents when compared with binary Fe-Cr systems. The precipitate morphology evolution with dose exhibited a transient coarsening regime akin to previously observed behavior in aged Fe-Cr alloys. Similar behavior to predictions of the LSW/UOKV models suggests that α^′ precipitation in irradiated FeCrAl is a diffusion-limited process with coarsening mechanisms similar to those in thermally aged high-Cr ferritic alloys.

Original language	English
Pages (from-to)	217-228
Number of pages	12
Journal	Acta Materialia
Volume	129
DOIs	https://doi.org/10.1016/j.actamat.2017.02.077
State	Published - May 1 2017

Funding

Primary research funding was sponsored by the US Department of Energy's (DOE) Office of Nuclear Energy, Advanced Fuel Campaign of the Fuel Cycle R&D Program. Neutron irradiation of FeCrAl alloys at ORNL's HFIR user facility was sponsored by the Scientific User Facilities Division, Office of Basic Energy Sciences, DOE. APT was conducted at the Center for Nanophase Materials Sciences, a DOE Office of Science User Facility, and at the Microscopy and Characterization Suite at the Center for Advanced Energy Studies at Idaho National Laboratory. A portion of this work was supported by DOE, Office of Nuclear Energy, under DOE Idaho Operations Office Contract DE-AC07-051D14517 as part of a Nuclear Science User Facilities experiment. A portion of funding for SAB was provided by the DOE Office of Nuclear Energy's Nuclear Energy University Programs.

Keywords

Atom probe tomography (APT)
Ferritic steels
Irradiated metals
Neutron diffraction
Precipitation

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10.1016/j.actamat.2017.02.077

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title = "A combined APT and SANS investigation of α′ phase precipitation in neutron-irradiated model FeCrAl alloys",

abstract = "FeCrAl alloys are currently under consideration for accident-tolerant fuel cladding applications in light water reactors owing to their superior high-temperature oxidation and corrosion resistance compared to the Zr-based alloys currently employed. However, their performance could be limited by precipitation of a Cr-rich α′ phase that tends to embrittle high-Cr ferritic Fe-based alloys. In this study, four FeCrAl model alloys with 10–18 at.% Cr and 5.8–9.3 at.% Al were neutron-irradiated to nominal damage doses up to 7.0 displacements per atom at a target temperature of 320 °C. Small angle neutron scattering techniques were coupled with atom probe tomography to assess the composition and morphology of the resulting α′ precipitates. It was demonstrated that Al additions partially destabilize the α′ phase, generally resulting in precipitates with lower Cr contents when compared with binary Fe-Cr systems. The precipitate morphology evolution with dose exhibited a transient coarsening regime akin to previously observed behavior in aged Fe-Cr alloys. Similar behavior to predictions of the LSW/UOKV models suggests that α′ precipitation in irradiated FeCrAl is a diffusion-limited process with coarsening mechanisms similar to those in thermally aged high-Cr ferritic alloys.",

keywords = "Atom probe tomography (APT), Ferritic steels, Irradiated metals, Neutron diffraction, Precipitation",

author = "Briggs, {Samuel A.} and Edmondson, {Philip D.} and Littrell, {Kenneth C.} and Yukinori Yamamoto and Howard, {Richard H.} and Daily, {Charles R.} and Terrani, {Kurt A.} and Kumar Sridharan and Field, {Kevin G.}",

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AU - Briggs, Samuel A.

AU - Edmondson, Philip D.

AU - Littrell, Kenneth C.

AU - Yamamoto, Yukinori

AU - Howard, Richard H.

AU - Daily, Charles R.

AU - Terrani, Kurt A.

AU - Sridharan, Kumar

AU - Field, Kevin G.

PY - 2017/5/1

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N2 - FeCrAl alloys are currently under consideration for accident-tolerant fuel cladding applications in light water reactors owing to their superior high-temperature oxidation and corrosion resistance compared to the Zr-based alloys currently employed. However, their performance could be limited by precipitation of a Cr-rich α′ phase that tends to embrittle high-Cr ferritic Fe-based alloys. In this study, four FeCrAl model alloys with 10–18 at.% Cr and 5.8–9.3 at.% Al were neutron-irradiated to nominal damage doses up to 7.0 displacements per atom at a target temperature of 320 °C. Small angle neutron scattering techniques were coupled with atom probe tomography to assess the composition and morphology of the resulting α′ precipitates. It was demonstrated that Al additions partially destabilize the α′ phase, generally resulting in precipitates with lower Cr contents when compared with binary Fe-Cr systems. The precipitate morphology evolution with dose exhibited a transient coarsening regime akin to previously observed behavior in aged Fe-Cr alloys. Similar behavior to predictions of the LSW/UOKV models suggests that α′ precipitation in irradiated FeCrAl is a diffusion-limited process with coarsening mechanisms similar to those in thermally aged high-Cr ferritic alloys.

AB - FeCrAl alloys are currently under consideration for accident-tolerant fuel cladding applications in light water reactors owing to their superior high-temperature oxidation and corrosion resistance compared to the Zr-based alloys currently employed. However, their performance could be limited by precipitation of a Cr-rich α′ phase that tends to embrittle high-Cr ferritic Fe-based alloys. In this study, four FeCrAl model alloys with 10–18 at.% Cr and 5.8–9.3 at.% Al were neutron-irradiated to nominal damage doses up to 7.0 displacements per atom at a target temperature of 320 °C. Small angle neutron scattering techniques were coupled with atom probe tomography to assess the composition and morphology of the resulting α′ precipitates. It was demonstrated that Al additions partially destabilize the α′ phase, generally resulting in precipitates with lower Cr contents when compared with binary Fe-Cr systems. The precipitate morphology evolution with dose exhibited a transient coarsening regime akin to previously observed behavior in aged Fe-Cr alloys. Similar behavior to predictions of the LSW/UOKV models suggests that α′ precipitation in irradiated FeCrAl is a diffusion-limited process with coarsening mechanisms similar to those in thermally aged high-Cr ferritic alloys.

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KW - Irradiated metals

KW - Neutron diffraction

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A combined APT and SANS investigation of α′ phase precipitation in neutron-irradiated model FeCrAl alloys

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