Recrystallization and texture evolution of cold pilgered FeCrAl cladding tube during annealing at 700 °C∼1000 °C

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.