In situ TEM observation of interactions between gliding dislocations and prismatic loops in Zr-ion irradiated zirconium alloys

Zirconium alloys cladding tubes containing the fuel of pressurized water nuclear reactors constitute the first barrier against the dissemination of radioactive elements. It is therefore essential to have a good understanding of the effects of neutron radiation on the deformation mechanisms of these materials. In order to study the effect of irradiation on the deformation mechanisms, zirconium alloys specimens have been irradiated with Zr ions at 350 °C and 500 °C. On these specimens in situ TEM tensile tests have been carried out at 350 °C and the interactions between gliding dislocations and radiation induced loops have been observed. It has been shown that in the case of edge dislocations gliding in prismatic planes, the loops can be incorporated within the dislocation as super-jog explaining the clearing of loops by gliding dislocations. However, it has also been shown that in specific configuration, the dislocation gliding in prismatic plane is strongly pinned by the loop, explaining the difficult activation of prismatic slip after irradiation resulting in the strong radiation induced hardening.