Crystallography of Hydrides in Textured Zircaloy-4 Sheets

Abstract

Cold-worked and stress-relieved (CWSR) Zircaloy-4 sheet-samples were charged with 45 to 247 ppm of hydrogen using an electrolytic technique. Optical microscopy shows stacks of hydride platelets oriented along the rolling direction of the samples. Morphology and orientation of the hydrides was examined using the Electron Backscatter Diffraction (EBSD) technique. The hydrides, identified as δZrH1.5 phase by the EBSD analysis, were located both within the grains and along the grain boundaries, but the grain boundary hydrides appeared to be dominant. The hydrides and the matrix have the (0001)α-Zr//(111)δZrH1.5 orientation relationship at all locations. Also, the hydrides show strong {111} texture with maxima located at the same angle on the pole figure as the maxima of basal plane of the α-zirconium matrix. The reproducibility of the results was verified using samples with different hydride concentrations.