Microstructural study of hydride formation in Zr–1Nb alloy

Abstract

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 ∥( 1 ̄ 1 1 ̄ ) δ and [1 1 2 ̄ 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 2 ̄ 1 0] α ∥[1 1 ̄ 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.