Dynamic behavior of a 6069 Al alloy under hot compression

The high temperature deformation behavior of a 6069 Al alloy was examined on a Gleeble 3500 thermal-mechanical simulation machine at temperatures ranging from 300 degrees C to 550 degrees C and strain rates varying between 0.001 s(-1) and 10 s(-1). The strain-hardening and dynamic softening mechanisms of the alloy were analyzed. Strain-hardening behavior was investigated using Kocks-Mecking type plots. Stage III hardening behavior occurred immediately after yielding under the deformation conditions performed in this study. Microstructural evolution analysis indicated that the softening mechanism at high strain rates or low temperatures proceeded via dynamic recovery. The net flow stress required for the onset of dynamic recovery increased with increasing strain rate or decreasing temperature. Partial dynamic recrystallization enhanced the softening effect at high temperatures with low strain rates. The microstructural evolution analyzed via electron backscatter diffraction showed that the operating mechanism of dynamic recrystallization was related to continuous dynamic recrystallization. A relative softening factor was used to quantify the effect of flow softening. The variations in the relative softening value with strain may be associated with hot deformation conditions, in which the flow stress behavior correlated with different microstructures and dynamic softening mechanisms. (C) 2015 Elsevier B.V. All rights reserved.