Characterization of Zircaloy-4 corrosion films using microbeam synchrotron radiation

The fraction of bulk tetragonal phase increased in the region located within one transition thickness near the oxide-metal interface. A strong periodicity was seen in oxide intensity from both the monoclinic and tetragonal phases corresponding to an oxide transition thickness of 1.8-1.9 μm. The grain size of the tetragonal phase was determined to be smaller than the monoclinic phase, and the grain size for the monoclinic phase decreased starting at a distance of approximately one transition layer from the oxide-metal interface. The relative amounts of monoclinic peak broadening due to strain and grain size were calculated, the former being approximately constant, while the latter decreased with increasing distance from the oxide-metal interface, corresponding to an increase in grain size. These findings are compared to previously performed microbeam diffraction experiments on Zircaloy-4 and other Zr-based alloys.