Evolution of microstructure during annealing of a severely deformed aluminum

The annealing behavior of a severely plastically deformed (SPD) aluminum, which was produced by equal channel angular extrusion (ECAE), was studied in the present work. The SPD structure is quite stable at temperatures below 523 K. As the annealing temperature increases, the grain growth rate exhibits a discontinuous change in the range of 548–573 K. The activation energy at lower annealing temperatures (<548 K) is 49 kJ/mol, while at higher temperatures (>573 K); it is 85 kJ/mol, which is close to the value for grain boundary diffusion in aluminum. The microstructures after annealing have been characterized quantitatively by the parameters including grain shape, grain size distribution, boundary misorientation and global texture. It is suggested that the annealing behavior of this SPD aluminum may be described as a continuous process of (sub)grain coarsening, or continuous recrystallization.