The role of plastic anisotropy in the fatigue behavior of zircaloy

Abstract

The changes in the plastic properties and the mode of fracture were examined with highly textured Zircaloy under strain-controlled push-pull cyclic loading condition. Since the loading direction was nearly normal to the (0002) poles of hcp structure, deformation occurred predominantly by prism slip. Different twinning systems were also activated when the sign of shear stress changed. The magnitude of plastic anisotropy also changed differently for warm cross-rolled and recrystallized materials. In spite of these structural anomalies, the Coffin-Manson relationship was obeyed, independent of the particular method used for control of diametral strain limits. Depending on the particular orientation of specimen surface, the process of crack initiation could be closely related to the detailed slip morphology. The crack propagation, however, occurred in the direction normal to the surface where the corresponding plastic strain range was the largest. Twinning was also shown to contribute importantly to the process of fracture in the cyclic loading condition.