| 1. |
- Qin, Xiao, 1993, et al.
(författare)
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Microstructure and texture evolutions in FeCrAl cladding tube during pilger processing
- 2023
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Ingår i: Journal of Materials Research and Technology. - 2238-7854. ; 25, s. 5506-5519
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Tidskriftsartikel (refereegranskat)abstract
- The microstructure of FeCrAl cladding tubes depends on the fabricating process history. In this study, the microstructural characteristics of wrought FeCrAl alloys during industrial pilger processing into thin-walled tubes were investigated. The hot extruded tube showed ∼100 μm equiaxed grains with weak α∗-fiber in {h11}<1/h12> texture, while pilger rolling process change the microstructure to fragmented and elongated grains along the rolling direction. The pilgered textures could be predicted with the VPSC model. The inter-pass annealing at 800–850 °C for 1 h results in recovery and recrystallization of the ferric matrix and restoration of ductility. The final finished tube shows fine recrystallized grains (∼11 μm) with dominant γ-fiber in three dimensions. Pilger rolling enhanced α-fiber while annealing reduced α-fiber and enhanced γ-fiber. Microstructural evolution in the Laves precipitates followed the sequence of faceted needle-like → spherical → faceted ellipsoidal. Thermomechanical processing resulted in cladding tubes with an area fraction of ∼5% and a number density of 5 × 10−11 m−2 in Laves precipitates, which is half that of the first-pilgered tube. Laves precipitates pin the grain boundaries to control the microstructure and prevent grain coarsening.
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| 2. |
- Qin, Xiao, 1993, et al.
(författare)
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Recrystallization and texture evolution of cold pilgered FeCrAl cladding tube during annealing at 700 °C∼1000 °C
- 2023
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Ingår i: Journal of Nuclear Materials. - : Elsevier BV. - 0022-3115. ; 577
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Tidskriftsartikel (refereegranskat)abstract
- FeCrAl alloys are being developed as potential accident-tolerant fuel cladding materials for the light water reactors due to significantly improved steam oxidation and good mechanical properties at high temperatures. In this study, the recrystallization and texture evolution of the cold pilgered FeCrAl cladding tube was investigated by means of hardness measurements and electron backscatter diffraction (EBSD) during annealing at 700∼1000 °C. The partially recrystallized maps were deconstructed into deformed, recovered, and recrystallized grain fractions based on the critical internal misorientation angle. In the early stages of recrystallization, cold pilgered cladding tubes contained a mixture of discontinuously recrystallized {111}<110> newly nucleated grains and heterogeneous deformed 〈110〉 orientation grains. The deformed microstructural inhomogeneity state could be explained based on the Taylor factor. The rate of recrystallization increased with increasing annealing temperature, which was described by the Johnson-Mehl-Avrami-Kolmogorov equation. The cladding tube showed slow recrystallization kinetics and thermally stable grains due to the pinning of the grain boundaries by the Laves precipitates. The dominant α-fiber decreased and γ-fiber increased with increasing recrystallization fraction in the cold pilgered tubes. The high area fraction and stable γ-fiber would be beneficial to the processability of the cladding tube.
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| 3. |
- Qin, Xiao, 1993, et al.
(författare)
-
Recrystallization and texture evolution of warm-pilgered FeCrAl alloy tube during annealing at 850°C
- 2022
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Ingår i: Journal of Nuclear Materials. - : Elsevier BV. - 0022-3115. ; 562
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Tidskriftsartikel (refereegranskat)abstract
- Recrystallization annealing of warm-pilgered FeCrAl tubes was the key to reduce the cracking and control the microstructure and properties of the cladding tube. The recrystallization and texture evolution of warm-pilgered FeCrAl tubes were investigated. The recrystallization kinetics and textural evolution during annealing were characterized using microhardness measurements and electron backscatter diffraction. The 3D-microstructure of the warm-pilgered FeCrAl tube exhibited heterogeneous deformed grains of α-fiber and γ-fiber orientation. The significant anisotropy results in different recrystallization kinetics in the axial and circumferential directions of the tube. The mirostructure maintains a stable grain size of ∼22 µm and an aspect ratio of 1.8 in the axial and circumferential directions within 0–600 min annealing time. The stable microstructure is due to the dispersion of fine Laves phase particles in the ferrite matrix. Quantitative texture analysis shows that the α-fiber texture decreased significantly and the γ-fiber increased after recrystallization. During the annealing process, the α-fiber strong point texture component {112}<110> turns into {223}<110> and the γ-fiber component {111}<110> turns into {111}<112>. The recrystallization and texture evolution of warm-pilgered FeCrAl tube is of great significance to preparation and microstructure control of final cladding tube.
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