Damage and stress state influence on the Bauschinger effect in aluminum alloys

In this paper, we show that the Bauschinger effect is intimately tied not only to plasticity as is historically understood but to the damage state as well. We illustrate the plasticity and damage influence on the Bauschinger effect by employing different definitions (Bauschinger stress parameter, Bauschinger effect parameter, the ratio of forward-to-reverse yield, and the ratio of kinematic-to-isotropic hardening) for two differently processed aluminum alloys (rolled and cast) in which specimens were tested to different prestrain levels under tension and compression. Damage progression from second phase particles and inclusions that were generally equiaxed for the cast A356-T6 Al alloy and elongated for the rolled 7075 Al alloy was quantified from interrupted experiments. Observations showed that the Bauschinger effect had larger values for compression prestrains when compared to tension. The Bauschinger effect was also found to be a function of damage to particles/inclusions, dislocation/particle interaction, and the work hardening rate.