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)α∥(1̄ 1 1̄)δ and [1 1 2̄ 0]α∥[1 1 0]δ. The orientation relationship between the α matrix and the γ-hydride was of the following type: (0 0 0 1)α∥(0 0 1)γ and [1 2̄ 1 0]α∥[1 1̄ 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.