Microstructural changes occurring during the fabrication of Zr-2.5 pct Nb alloy pressure tubes by a modified route, involving hot extrusion followed by two pilgering operations with an intermediate annealing step, have been examined in detail. In the conventional fabrication route, the hot extrusion step is followed by a single cold drawing operation in which the cold work to the extent of 25 pct is imparted to the material for achieving the required mechanical properties. Tensile properties obtained at each stage of fabrication have been evaluated and compared between the two processes. The main aim of this work has been to produce a microstructure and texture which are known to yield a lower irradiation growth. Additionally, suitable annealing conditions have been optimized for the intermediate annealing which annihilates the cold work introduced by the first cold pilgering operation without disturbing the two-phase elongated microstructure. This elongated α+ β
 I
 microstructure is required for obtaining the desired level of strength at 310 °C. The final microstructure and the crystallographic texture of the finished pressure tube have been compared with those reported for the conventionally processed material.

Evolution of microstructure during fabrication of Zr-2.5 Wt pct Nb alloy pressure tubes

Hydrogen detection near surfaces and shallow interfaces with resonant nuclear reaction analysis

Precipitation morphology and habit planes of the delta-phase Zr hydrides, which were precipitated within the a-phase matrix grains and along the grain boundaries of recrystallized Zircaloy-2 cladding tube, have been examined by electron backscatter diffraction (EBSD). Radially-oriented hydrides, induced by residual tensile stress, precipitated in the outside region of the cladding, and circumferentially-oriented hydrides in the stress-free middle region of the cladding. The most common crystallographic relationship for both types of the hydrides precipitated at the inter- and intra-granular sites was identical at (0001)(alpha) // {111}(delta), with {1017}(alpha) // {111}(delta) being the occasional exception only for the inter-granular radial hydrides. When tensile stress was loaded, the intra-granular hydrides tended to preferentially precipitate in the grains with circumferential basal pole textures. The inter-granular hydrides tended to preferentially precipitate on the grain faces opposite to tensile axis. The change of prioritization in the precipitation sites for the hydrides due to tensile stress could be explained in terms of the relaxation effect of constrained elastic energy on the terminal solid solubility of hydrogen at hydride precipitation.

https://www.tandfonline.com/doi/pdf/10.1080/18811248.2004.9715540

Crystallography of Zirconium Hydrides in Recrystallized Zircaloy-2 Fuel Cladding by Electron Backscatter Diffraction

Intergranular δ-hydride nucleation and orientation in zirconium alloys

G.C. Weatherly

Papers

The nucleation of hydrides in a Zr-2.5 wt% Nb alloy

Characterization of Dislocation Substructures in Zr-2.5 Nb Pressure Tube Alloys

Hydrogen and deuterium profiling at the surface of zirconium alloys: II. The effects of oxidation

Thermal Diffusion of Hydrogen and Hydride Precipitation in Zr–Nb Pressure Tube Alloys

Hydrogen and deuterium profiling at the surface of zirconium alloys: I. The effects of surface preparation