The study of hardening evaluation of pure Zr with δ-hydrides generation by the dynamic in-situ metallic structure observation and nano-indentation hardness test

The in-situ TEM observations during tensile tests, electron backscatter diffraction (EBSD) analyses and nano-indentation hardness tests were performed to investigate the hardening mechanism by the relationship between the slip planes of dislocations and the habit planes of δ-hydrides in the pure Zr. The δ-hydride of habit plane which has crystal orientation relationship of (0001)α plane//{111}δ plane and <21¯1¯0>α direction//<110>δ direction, was generated in pure Zr sample. The α-Zr phase was hardened on the crystal orientation of mainly (0001)α plane slip of dislocation. The hardening depends on crystal orientation and it was influenced by the interaction area (sheared area) of dislocations and δ-hydrides. It suggests that the hardening depends on the deference between the slip plane of dislocation and the habit plane of δ-hydride. Also, the hardening of pure Zr was influenced by the δ-hydride but not by the solid solution hydrogen. It is considered that the failure and embrittlement with the δ-hydrides generation in pure Zr is more influenced by the orientation of the long axis direction of δ-hydride than the interaction between the dislocation and δ-hydride in the α-Zr phase.