Effect of neutron irradiation on microstructural evolution and deformation behavior of Zirconium (Zr-1Nb) alloy

In this study, a detailed investigation was carried out on the recrystallized Zirconium (Zr-1Nb) alloy, irradiated in the reactor core of Temelín NPP (VVER-1000) for a duration of four annual cycles within the framework of the ALVEL-ČEZ project. The main objective of the present work is to report the microstructural evolution, with a particular focus on the radiation-induced defects and elucidate the underlying deformation mechanisms. The combined use of electron backscattered diffraction and scanning transmission electron microscopy enables to obtain the statistical details of the microstructural changes in the irradiated material. To assess the deformation behavior of the irradiated Zr-1Nb alloy, tensile testing was conducted at room temperature and 350°C and a strain rate of 2 × 10-3 s-1 along the axial direction of the tube. Transmission electron microscopy observations on the deformed sample revealed the presence of dislocation-free channels within the grains. Based on the stereographic trace analysis, it was determined that slip occurred through prismatic, pyramidal and basal channels. Additionally, the { 01 1 ¯ 1 } 〈 0 1 ¯ 12 〉 type twinning system was also found to be activated in the deformed sample.