In Situ TEM Observation of Growth Process of Zirconium Hydride in Zircaloy-4 during Hydrogen Ion Implantation

Abstract

In situ observation during hydrogen ion implantation was performed with a transmission electron microscope installed in an ion accelerator to investigate the growth process of Zr hydride in Zircaloy-4. To clarify the effect of radiation damage, some samples were irradiated with 4 MeV Ni3+ ions prior to hydrogen implantation. Growth processes of Zr hydrides accompanying the formation of dislocations were observed. The crystallographic relationship between the Zr matrix and Zr hydrides was identical with that found in previous studies: inter- and intragranular hydrides exhibiting a tendency to grow in the (112-0) direction. This growth can be attributed to a shear mechanism in which there are partial dislocations along basal planes. In specimens preirradiated with Ni ions, the growth rate of hydrides was suppressed, but the growth direction was not affected by radiation defects. It was also confirmed that the black spots induced by Ni3+ ion irradiation grew during hydrogen ion implantation, suggesting the formation of hydrides at the defects.