EBSD analysis on restoration mechanism of as-extruded AA2099 Al-Li alloy after various thermomechanical processes

- Processing map is established for an as-extruded AA2099 Al-Li alloy.
- Stored energy calculation is performed to discriminate restoration mechanisms.
- DDRX is confirmed to occur in specimens with low Zenner-Holloman parameters.
- Power dissipation efficiency is demonstrated to relate to the restoration mechanisms.

Cylindrical specimens of as-extruded AA2099 Al-Li alloy are uniaxially compressed at temperatures ranging from 360 °C to 520 °C and strain rates ranging from 0.001 s−1 to 10 s−1. Processing map of these specimens was established. Electron backscatter diffraction (EBSD) measurements were performed for specimens deformed under various conditions to probe their microstructures and restoration mechanisms. Stored energies in various specimens are calculated based on statistics of low angle boundaries via EBSD data. The remarkable decrement of stored energy and misorientation characteristics reveal that dynamic recrystallization (DRX) happens at 480-520 °C and 0.001-0.1 s−1. Obvious DRX nucleation further suggests that this process should be classified to discontinuous dynamic recrystallization (DDRX). Stored energies in various specimens strongly affect the extents of dynamic recovery and dynamic recrystallization. By systemically considering the processing map and restoration behaviours of the specimens, the dynamic recrystallization regimes and the central high-η regimes are determined to correspond to preferable thermo-mechanical processing parameters for the as-extruded AA2099 Al-Li alloy.

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