The effect of recovery annealing after small plastic deformations on the yield strength of polycrystalline aluminium

Abstract

Investigations of the yield strenght of polycrystalline aluminium have been performed, looking at the effect of recovery annealing after small plastic deformations. The kinetics of the yield strength changes were determined as a function of temperature and time. Results were discussed in relation to electron microscopy observations of changes in the microstructure. It has been found that changes in the yield strength in fine-grained aluminium after small plastic deformations and recovery annealing are controlled by the mechanisms on grain boundaries whereas in coarse-grained aluminium the most important effects are associated with mechanisms in the grain interior. In fine-grained aluminium these mechanisms are: the annihilation of dislocations in grain boundaries which leads to a decrease of the total dislocation density, and the change of the grain boundary characteristics enhanced by this annihilation. In coarse-grained polycrystal the basic mechanisms are rearrangement of tangled dislocations and dislocation walls into subboundaries and growth of subgrains.