Mechanism on Annealing Recrystallization of Al-Zn-Mg-Cu-Sc Alloy

Microstructure and recrystallization behaviour were studied for a sort of Al-Zn-Mg-Cu-Sc alloy in different conditions by means of OM and SEM with EDS and TEM, as well as using topology for grain and boundary. The results show that the recrystallization temperature can be obviously increased with addition of 0.15%Sc to base alloy. The course of recrystallization is speeded up with increasing the velocity of strain at a constant total distortion. Under the condition of dissymmetrical deformation, there are some shear bands or cracks in the region, which can be looked as an "empty zone" without any solute or solvent. It is found that the deformation boundary bending leads to recrystallization nucleation, and the subgrain rotation coalescence leads to growth. The "secondary crystal" is accomplished by the assembly of solute or solvent atoms entering the "empty zone" by diffusing, with a lot of vacancies and solute atoms segregating in the vacancies.