Overview of fatigue properties of fine grain 5056 Al-Mg alloy processed by equal-channel angular pressing

The fatigue performance of the fine-grain 5056 Al-Mg alloy processed by severe plastic deformation through equal-channel angular pressing (ECAP) is assessed in both stress- and plastic strain-controlled experiments. Compared to its conventional counterpart, the ECAP material exhibits a high tensile and low-cyclic fatigue strength under constant stress amplitude. However, its fatigue life under strain-controlled conditions is notably shorter than that of the O-temper specimens. Despite severe pre-straining of the specimen during ECA-pressing, cyclic softening was found to be rather small. It is shown that the mechanical characteristics obtained after ECAP can be significantly improved during short time annealing at moderate temperatures (150°C, 15 min) after fabrication. Such heat treatment is supposed to recover partially the grain boundary region, which has been most heavily distorted during processing. Mechanisms of fatigue in ECA-processed materials are discussed within a framework of a simple one-parametric model of dislocation kinetics.