Microstructural study of hydride formation in Zr-1Nb alloy

Hydriding of Zr-1Nb alloy having a microstructure comprising equiaxed α grains and a uniform distribution of spherical particles of the β-phase has been carried out in this study. The specimens were hydrided by gaseous charging method to different hydrogen levels. The microstructures of hydrided samples were examined as a function of hydrogen content. The formation of δ-hydride in slow cooled specimens and formation of γ-hydride in rapidly cooled specimens has been studied with their morphology, habit plane and orientation relationship with the α matrix in view. The habit planes of either type of hydride phase has been determined and compared with those observed in other Zr-Nb alloys. The orientation relationship between the α matrix and the δ-hydride was found to be the following: (0 0 0 1)αparallel(1-bar 1 1-bar)δ and [1 1 2-bar 0]αparallel[1 1 0]δ. The orientation relationship between the α matrix and the γ-hydride was of the following type: (0 0 0 1)αparallel(0 0 1)γ and [1 2-bar 1 0]αparallel[1 1bar 0]γ. The internal structure of both types of hydride has been examined. The effect of the presence of the spherical β-phase particles in the α matrix on the growth of the hydride plates has been investigated