DRX in 7050 aluminum alloy during constraint deformation processing at high temperature

Combined extrusion experiment (including direct and indirect extrusion) at 440 for large amount of deformation was carried out with the solution treated AA7050 aluminum alloy. Qualitative description and quantitative characterization were conducted employing electron backscattered diffraction (EBSD) technique on the microstructure of typical regions with different filler contents. These characteristic regions were filled at the following stages: ahead of filling (AF), beginning of filling (BF), mid stage of filling (MF) and the end of filling (EF). EBSD results showed that recrystallization fraction during direct extrusion were 8.3%, 13.5%, 9.3% and 11.2%, for AF, BF, MF and EF, respectively. Recrystallization fraction during indirect extrusion were 15.5%, 9.1% 5.2% and 9.9%, for AF, BF, MF and EF, respectively. It shows that the mode and the amount of deformation played an important role in DRX. DRX grains were formed continuously during direct extrusion, while during indirect extrusion, fewer DRX grains generated, and only originally generated DRX grains grew larger gradually.