Effects of Zn Addition on Dynamic Recrystallization of High Strain Rate Rolled Al–Mg Sheets

Effects of Zn addition (0, 0.5, 1.0 and 1.5 wt%) on dynamic recrystallization (DRX) behavior of Al-9.2Mg alloy during high strain rate rolling (with rolling temperature of 400 °C and strain rate of 8.6 s−1) are carefully investigated. The Zn content plays a significant role in the enhanced DRX of Al-9.2Mg alloy. The critical strain (ec) and the peak strain (ep) are reduced from 0.178 ± 0.002 to 0.102 ± 0.001 and 0.211 ± 0.003 to 0.139 ± 0.002 with the Zn content increasing from 0 to 1.5%, respectively. Almost complete DRX grains are obtained in the Al-9.2Mg-0.5Zn alloy. The DRX volume fraction (FDRX), the average DRX grain size (AGS), the volume fraction of high-angle grain boundaries (FHAGBs) and the average grain boundary angle (θAV) are 91.5%, 5.6 μm, 91.1% and 37.6 o, respectively. The Zn addition can enhance the formation of deformation bands (DBs) and promote the DRX process by providing the nucleation sites for new grains, while the increased dynamic precipitates inhibit DRX. Continuous dynamic recrystallization (CDRX) is the dominant DRX mechanism, while discontinuous dynamic recrystallization (DDRX) is also existent. Effects of Zn addition on DRX process of the Al–Mg alloys can be ascribed to the more DBs, the reduced stacking fault energy (SFE) and the dynamic precipitates.