Influence of dynamic strain aging on the dislocation structure developed in Zircaloy-4 during low-cycle fatigue

Low-cycle fatigue tests between 573 and 873 K were carried out with a total strain range of 1% in order to study the cyclic behaviour and dislocation structure developed in Zircaloy-4. According to them, three ranges of temperature have been distinguished: low, intermediate and high. The intermediate one is characterized by the activation of a dynamic strain aging process which is manifested mechanically by an incremental rate of cyclic hardening and microstructurally by a pronounced increase in the dislocation density. In order to analyse the dislocation dynamics on the evolution of the microstructure, interrupted tests have been performed. These results have been used to propose a model of dislocation glide and accumulation for a hexagonal metal. (C) 2004 Elsevier B.V. All rights reserved.