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

The fatigue performance of the fine-grain 5056 Al-Mg alloy processed by sev ere plastic deformation through equal-channel angular pressing (ECAP) is as sessed 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, i ts fatigue life under strain-controlled conditions is notably shorter than that of the O-temper specimens. Despite severe pre-straining of the specime n during EGA-pressing, cyclic softening was found to be rather small. It is shown that the mechanical characteristics obtained after ECAP can be signi ficantly improved during short time annealing at moderate temperatures (150 degreesC, 15 min) after fabrication. Such heat treatment is supposed to re cover partially the grain boundary region, which has been most heavily dist orted during processing. Mechanisms of fatigue in EGA-processed materials a re discussed within a framework of a simple one-parametric model of disloca tion kinetics. (C) 2001 Elsevier Science B.V. All rights reserved.