Effect of loading direction on the deformation and annealing behavior of a zirconium alloy

Zr alloys are used as cladding materials in nuclear reactor, and new alloys and process are continuously developing. This work focuses on the influence of loading direction on deformation and subsequent annealing behavior of hexagonal Zr-4 alloy. As-received Zr-4 sheets with recrystallized microstructure and strong crystallographic texture were compressed along the normal direction (ND) and rolling direction (RD) at room temperature. Different strain levels were applied and subsequent annealing at various temperatures was carried out. Microstructures and textures were characterized by electron backscatter diffraction (EBSD) method. For a same strain level, the fraction of low angle misorientation is higher after ND compression than RD compression, indicating higher stored dislocation density. During annealing, obvious recrystallization causes grain growth in ND compressed specimens when the annealing temperature is higher than 650 °C, while no significant recrystallization happens in RD compressed specimens, even annealed at 700 °C. Visco-plastic self-consistent (VPSC) simulations are used to evaluate the type of stored dislocations, their density and the stored energy, and explain the different annealing behaviors after ND compression and RD compression.