Microstructural Origin of Residual Stress Relief in Aluminum

Annealing-induced microstructural evolution and associated stress relief were investigated experimentally for various crystallographic orientations and annealing temperatures. Combinations of the site and orientation-specific X-ray plus electron diffraction were used. 2-D discrete dislocation dynamics, oriented for double slip with both dislocation glide and climb mechanisms, was employed to simulate the annealing process. Irrespective of crystal orientation, both experiments and simulations showed the highest stress relief at the intermediate annealing temperature. In the experiments, this was related to the fastest elimination of low angle grain boundaries. In the simulations, it was linked to the largest reduction in the density of pinned dislocations. The simulations also suggested that the non-monotonic temperature dependence of the stress relief, and associated substructural changes, emerged from a balance between dislocation glide and climb processes.