Molecular dynamics simulations of the effects of annealing on the micro residual stress induced by vacancy defects in aluminum crystal

•Maximum range of residual stress change is approximately linear with void radius.•Atomic stress near void of different sizes changes differently during annealing.•Atomic distributions near void are more uniform and regular after annealing.•Different sizes of voids affect atomic potential energy and stress differently. Micro residual stress induced by vacancy defects in aluminum crystals was studied by molecular dynamics. The effects of different sizes of vacancy defects on the initial configuration (stable configuration after energy minimization) are analyzed, which are reflected by the changes of atomic potential energy, atomic displacement and atomic stress. The influence of annealing on the lattice structure of atoms near the vacancy defects and the evolution of the defects in the annealing process are also analyzed. After annealing, the vacancies are filled and the atomic lattice structures near the vacancy also change, adding a HCP lattice structure. The atomic distributions are more uniform and more regular. When the voids are small, the atomic stress decreases obviously after annealing. However, when the voids are large, the atomic stress increases after annealing. The influence range of vacancy defects on the micro residual stress is a spherical space with the center of the void as the center of the sphere, and the radius of the sphere is linear relationship with the radius of the voids. When the void radius is small, the annealing heat treatment method can effectively eliminate or reduce the micro residual stress. When the void radius exceeds threshold value, the micro residual stress increases after annealing. A single annealing heat treatment method cannot effectively eliminate the residual stress, which may need to be combined with other methods to eliminate or reduce the residual stress.