Volume 7, Issue 9 (October 2010)
Texture Evolution of Zircaloy-2 During Beta-Quenching: Effect of Process Variables
The nuclear industry is interested in developing thermomechanical processes to produce random crystallographic orientation (texture) from cold-rolled Zircaloy-2 sheets used to manufacture boiling water reactor (BWR) channels. Randomized textures are beneficial because they minimize anisotropic irradiation-assisted growth, which in turn reduces bowing and uncontrolled deformation of BWR channels during service. The texture evolution of cold-rolled Zircaloy-2 sheets during the allotropic α→β→α phase transformation was characterized by using synchrotron X-ray diffraction in situ and electron backscatter diffraction. The initial strong rolling texture is weakened only if the α→β→α phase transformation is complete. Plastic deformation and grain growth in the β-phase lead to changes in the β texture and modify the inherited α texture. The global texture evolution is not sensitive to levels of stress that do not cause β plastic deformation. These findings demonstrate that accurate temperature control of the β-quenching process is of utmost importance in order to minimize undesirable irradiation growth of BWR channels during service, and that plastic deformation in the β phase can be employed to modify the inherited α texture. BWR channels with β-quenched textures will exhibit minimum irradiation growth caused by texture.