Serrated flow behavior in 2090 Al-Li alloy influenced by texture and microstructure

The center- and surface-layer specimens of 2090 Al-Li alloy plate was solution-treated, peak-aged, or reversion-treated. The flow stresses of the center layer specimens were higher than those of the surface-layer specimens, regardless of the heat treatments. The textures of the surface-layer specimens were approximated by the {0 0 1}〈1 1 0〉 orientation, while those of the center-layer specimens were approximated by the {0 1 1}〈2 1 1〉 orientation. Both the surface- and center-layer specimens of the solution-treated alloy gave rise to extensive serrations in their flow curves at a strain rate of 2 × 10−4 s−1. For the peak-aged alloy with spherical δ′ precipitates, the surface-layer specimen underwent serrated flows, whereas the flow curves of the center-layer specimen were devoid of serration. Serrated flows occurred in both the surface-layer and center-layer specimens of reversion-treated alloy with plate-like T1 precipitates. The findings are discussed in terms of the texture, microstructure, serration characteristics, and kinetics of the onset of serrated flows. The study results indicate that the serrated flow of the Al-Li alloy cannot be explained by a single mechanism, but can be attributed to both the shearing of δ′ or T1 precipitates and dynamic strain aging.