Dynamic precipitation and its effect on microstructure of 2195 Al-Li alloy during medium/high temperature deformation

In this work, the homogenized Al-Li alloys were compressed at different strains (20%-80%) under medium (370degree celsius) and high temperatures (470degree celsius), and their microstructures were characterized by SEM, EBSD, and TEM. The evolution of dynamic precipitation (DPN) during thermal deformation and its effect on microstructure and flow behavior were investigated. The results show that obvious flow softening appears with the increase of strain at medium temperature deformation while not at high temperatures, associated with the reduction of solid solution strengthening caused by DPN and the fragmentation of T-1 precipitates with large aspect ratios. The T-1 precipitates undergo fragmentation, dissolution and re-precipitation to develop two types of T-1 bands. Deformation at medium temperatures, DPN inhibits dislocations and (sub)grain boundary movement, and mainly dynamic recovery (DRV) accompanied by little dynamic recrystallization (DRX) occurs. The fine secondary phases at high temperatures are dominated by the pre-existing Al3Zr phase, and some precipitates are observed until 80% strain, however, DPN has little influence on precipitation hardening and DRX and occurs later than DRX. DRX mechanism changes from CDRX (20-60%) to CDRX and GDRX (80%) with strain at high temperatures. Furthermore, the deformed grains tend to develop in <101>//CD (compression direction) fiber texture during deformation, and the texture strength increases with increasing strain and decreasing temperature.