TY - JOUR
T1 - Influence of grain size on α′ Cr precipitation in an isothermally aged Fe-21Cr-5Al alloy
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
N1 - Publisher Copyright:
© 2024 Acta Materialia Inc.
PY - 2024/5
Y1 - 2024/5
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.
KW - Atom probe tomography
KW - Cr rich α′ precipitation
KW - Grain boundaries
KW - Iso-thermal Aging
KW - Nano structured FeCrAl alloys
KW - Sever plastic deformation
UR - http://www.scopus.com/inward/record.url?scp=85188714881&partnerID=8YFLogxK
U2 - 10.1016/j.mtla.2024.102047
DO - 10.1016/j.mtla.2024.102047
M3 - Article
AN - SCOPUS:85188714881
SN - 2589-1529
VL - 34
JO - Materialia
JF - Materialia
M1 - 102047
ER -