Recrystallization behavior of GH720 Li alloy in the γ+γ'bi-model phase region

The microstructure characteristics and recrystallization mechanism of GH720Li alloy deformed in the bi-model phase region and then air cooled or annealed were investigated by metalloscopy, scanning electron microscopy and transmission electron microscopy. It is found that the main softening mechanism after hot deformation at 1100℃ and air cooling is recovery and recrystallization occurs only in a limited portion of grains with the subgrain growth and merging mechanism due to a great content of gamma prime phase in the alloy. During the annealing process, the nucleation of static recrystallization may occur in dislocation pile-up areas located at the juncture of several grains or by strain-induced boundary migration (SIBM) but the whole recrystallizing process is restrained by the retained percentage of primary gamma prime phase. It must be pointed that the retained primary gamma prime phase in GH720Li can also be somewhat deformed during hot working and then also softened to some extent by recovery and recrystallization during the annealing process.