Abstract:

The strongly anisotropic mechanical behaviors commonly observed in Zr-4 sheets typically lead to inferior formability. In this study, the mechanical behavior and texture evolution of a cold-rolled Zr-4 sheet under uniaxial tension in various directions were systematically investigated, and the results showed both anisotropic yielding and hardening behavior in the Zr-4 sheet. The microstructure and texture features revealed by electron backscattered diffraction (EBSD) method indicate that this anisotropic mechanical behavior is closely related to the initial texture and its evolution during plastic deformation. In conjunction with experimental observations, a visco-plastic self-consistent (VPSC) model was employed to quantitatively analyze the relationship between the mechanical anisotropy and the texture features and activation of deformation modes. It was found that the yield anisotropy is affected by the distinct activity of prismatic <a> slip, while the different activities of basal <a> slip and extension twinning (ETW) result in anisotropic hardening. The distinct activation of deformation modes is mainly caused by differences in the evolution of the Schmid factor (SF) and critical resolved shear stress (CRSS) with increasing strain. Additionally, the results prove that the limited twinning activation with a fraction of less than 3% plays a non-negligible role in the hardening behavior during tension along the transverse direction. The latent hardening effect caused by the interaction between prismatic slip and tensile twinning is considered to successfully capture the anisotropic hardening behavior of the Zr-4 sheet. The implementation and insights from the predictions are presented and discussed in this work.

Key words: Zr-4 sheet, Anisotropic hardening, Texture evolution, Deformation modes, Twinning