Influence of grain size on α′ Cr precipitation in an isothermally aged Fe-21Cr-5Al alloy

Maalavan Arivu; Andrew Hoffman; Jonathan Poplawsky; Ian Spinelli; Cong Dai; Raul B. Rebak; James Cole; Rinat K. Islamgaliev; Ruslan Z. Valiev; Haiming Wen

doi:10.1016/j.mtla.2024.102047

Influence of grain size on α′ Cr precipitation in an isothermally aged Fe-21Cr-5Al alloy

Maalavan Arivu, Andrew Hoffman, Jonathan Poplawsky, Ian Spinelli, Cong Dai, Raul B. Rebak, James Cole, Rinat K. Islamgaliev, Ruslan Z. Valiev, Haiming Wen

Materials MicroAnalysis

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2 Scopus citations

Abstract

Cr-rich α′ precipitation during aging typically leads to hardening and accordingly embrittlement of FeCrAl alloys, which needs to be suppressed. The influence of grain size on α′ precipitation was studied by aging coarse-grained (CG), ultra-fine grained (UFG), and nanocrystalline (NC) ferritic Kanthal-D [KD; Fe-21Cr-5Al (wt.%) alloy] at 450, 500 and 550 °C for 500 h. After aging at 450 and 500 °C, less hardening was observed in the UFG KD than in CG KD. Atom probe tomography indicated a lower number density and larger sized intragranular α′ in the UFG versus the CG alloy. The smaller grain size and higher defect (vacancy and dislocation) density in the UFG KD facilitated diffusion and accordingly enhanced precipitation kinetics, leading to coarsening of precipitates, as well as saturation of precipitation at lower temperatures, as compared to those in CG KD. No hardening occurred in UFG and CG KD after aging at 550 °C, indicating that the miscibility gap is between 500 and 550 °C. NC KD exhibited softening after aging owing to grain growth. α′ precipitation occurred in NC KD aged at 450 °C but not at 500 °C, indicating that miscibility gap is between 450 and 500 °C. Thus, the significantly smaller grain size in NC KD decreased the miscibility gap, as compared to that in CG and UFG KD. This is attributed to the absorption of vacancies by migrating grain boundaries during aging, suppressing α′ nucleation and enhancing Cr solubility.

Original language	English
Article number	102047
Journal	Materialia
Volume	34
DOIs	https://doi.org/10.1016/j.mtla.2024.102047
State	Published - May 2024

Funding

This research was financially supported by U.S. Department of Energy, Office of Nuclear Energy through the NEET-NSUF (Nuclear Energy Enabling Technology - Nuclear Science User Facility) program (award number DE-NE0008524). Partial support for H. Wen came from the U.S. National Science Foundation (award number DMR-2207965). R. Islamgaliev is grateful to the Russian Science Foundation in the framework of the Project No. 22-23-00714. R.Z. Valiev acknowledges the support in part by the Ministry of Science and Higher Education of Russian Federation (Agreement No. 075-15-2022-1114 as of 06/30/2022). APT research was supported by the Center for Nanophase Materials Sciences (CNMS), which is a US Department of Energy, Office of Science User Facility at Oak Ridge National Laboratory. The authors would like to thank James Burns for his assistance in performing APT sample preparation and running the APT experiments. The MD simulation was funded by Atomic Energy of Canada Limited, under the auspices of the Federal Nuclear Science and Technology Program. Computational resources for the MD simulation work described in this paper were supported by the High-Performance Computing Cluster at Canadian Nuclear Laboratories.

Keywords

Atom probe tomography
Cr rich α′ precipitation
Grain boundaries
Iso-thermal Aging
Nano structured FeCrAl alloys
Sever plastic deformation

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10.1016/j.mtla.2024.102047

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title = "Influence of grain size on α′ Cr precipitation in an isothermally aged Fe-21Cr-5Al alloy",

abstract = "Cr-rich α′ precipitation during aging typically leads to hardening and accordingly embrittlement of FeCrAl alloys, which needs to be suppressed. The influence of grain size on α′ precipitation was studied by aging coarse-grained (CG), ultra-fine grained (UFG), and nanocrystalline (NC) ferritic Kanthal-D [KD; Fe-21Cr-5Al (wt.%) alloy] at 450, 500 and 550 °C for 500 h. After aging at 450 and 500 °C, less hardening was observed in the UFG KD than in CG KD. Atom probe tomography indicated a lower number density and larger sized intragranular α′ in the UFG versus the CG alloy. The smaller grain size and higher defect (vacancy and dislocation) density in the UFG KD facilitated diffusion and accordingly enhanced precipitation kinetics, leading to coarsening of precipitates, as well as saturation of precipitation at lower temperatures, as compared to those in CG KD. No hardening occurred in UFG and CG KD after aging at 550 °C, indicating that the miscibility gap is between 500 and 550 °C. NC KD exhibited softening after aging owing to grain growth. α′ precipitation occurred in NC KD aged at 450 °C but not at 500 °C, indicating that miscibility gap is between 450 and 500 °C. Thus, the significantly smaller grain size in NC KD decreased the miscibility gap, as compared to that in CG and UFG KD. This is attributed to the absorption of vacancies by migrating grain boundaries during aging, suppressing α′ nucleation and enhancing Cr solubility.",

keywords = "Atom probe tomography, Cr rich α′ precipitation, Grain boundaries, Iso-thermal Aging, Nano structured FeCrAl alloys, Sever plastic deformation",

author = "Maalavan Arivu and Andrew Hoffman and Jonathan Poplawsky and Ian Spinelli and Cong Dai and Rebak, {Raul B.} and James Cole and Islamgaliev, {Rinat K.} and Valiev, {Ruslan Z.} and Haiming Wen",

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doi = "10.1016/j.mtla.2024.102047",

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AU - Arivu, Maalavan

AU - Hoffman, Andrew

AU - Poplawsky, Jonathan

AU - Spinelli, Ian

AU - Dai, Cong

AU - Rebak, Raul B.

AU - Cole, James

AU - Islamgaliev, Rinat K.

AU - Valiev, Ruslan Z.

AU - Wen, Haiming

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N2 - Cr-rich α′ precipitation during aging typically leads to hardening and accordingly embrittlement of FeCrAl alloys, which needs to be suppressed. The influence of grain size on α′ precipitation was studied by aging coarse-grained (CG), ultra-fine grained (UFG), and nanocrystalline (NC) ferritic Kanthal-D [KD; Fe-21Cr-5Al (wt.%) alloy] at 450, 500 and 550 °C for 500 h. After aging at 450 and 500 °C, less hardening was observed in the UFG KD than in CG KD. Atom probe tomography indicated a lower number density and larger sized intragranular α′ in the UFG versus the CG alloy. The smaller grain size and higher defect (vacancy and dislocation) density in the UFG KD facilitated diffusion and accordingly enhanced precipitation kinetics, leading to coarsening of precipitates, as well as saturation of precipitation at lower temperatures, as compared to those in CG KD. No hardening occurred in UFG and CG KD after aging at 550 °C, indicating that the miscibility gap is between 500 and 550 °C. NC KD exhibited softening after aging owing to grain growth. α′ precipitation occurred in NC KD aged at 450 °C but not at 500 °C, indicating that miscibility gap is between 450 and 500 °C. Thus, the significantly smaller grain size in NC KD decreased the miscibility gap, as compared to that in CG and UFG KD. This is attributed to the absorption of vacancies by migrating grain boundaries during aging, suppressing α′ nucleation and enhancing Cr solubility.

AB - Cr-rich α′ precipitation during aging typically leads to hardening and accordingly embrittlement of FeCrAl alloys, which needs to be suppressed. The influence of grain size on α′ precipitation was studied by aging coarse-grained (CG), ultra-fine grained (UFG), and nanocrystalline (NC) ferritic Kanthal-D [KD; Fe-21Cr-5Al (wt.%) alloy] at 450, 500 and 550 °C for 500 h. After aging at 450 and 500 °C, less hardening was observed in the UFG KD than in CG KD. Atom probe tomography indicated a lower number density and larger sized intragranular α′ in the UFG versus the CG alloy. The smaller grain size and higher defect (vacancy and dislocation) density in the UFG KD facilitated diffusion and accordingly enhanced precipitation kinetics, leading to coarsening of precipitates, as well as saturation of precipitation at lower temperatures, as compared to those in CG KD. No hardening occurred in UFG and CG KD after aging at 550 °C, indicating that the miscibility gap is between 500 and 550 °C. NC KD exhibited softening after aging owing to grain growth. α′ precipitation occurred in NC KD aged at 450 °C but not at 500 °C, indicating that miscibility gap is between 450 and 500 °C. Thus, the significantly smaller grain size in NC KD decreased the miscibility gap, as compared to that in CG and UFG KD. This is attributed to the absorption of vacancies by migrating grain boundaries during aging, suppressing α′ nucleation and enhancing Cr solubility.

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KW - Cr rich α′ precipitation

KW - Grain boundaries

KW - Iso-thermal Aging

KW - Nano structured FeCrAl alloys

KW - Sever plastic deformation

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JO - Materialia

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ER -

Influence of grain size on α′ Cr precipitation in an isothermally aged Fe-21Cr-5Al alloy

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