Controlling mechanisms of deformation of AA5052 aluminium alloy at small strains under hot working conditions

The objective of the present work was to investigate the thermomechanical behaviour of a commercial Al-Mg alloy and to understand the deformation mechanisms taking place at small strains (<0.2) and high temperatures (≥300 °C) at strain rates relevant to hot working conditions (0.01-10 s−1). The experimental approach addresses different effects of testing machines on the load-displacement measurements. The results show distinct sorts of behaviour depending on the Zener-Hollomon parameter (Z): normal continuous increase in the stress with strain for high values of Z and a rise followed by a drop in stress with increasing strain for low values of Z. For steady-state behaviour, the relationship between stress and strain rate follows the typical power law with an exponent of 3 at low values of Z and an exponential relationship at higher values. These observations are similar to those of creep. The difference in stress response may be explained by different controlling mechanisms, namely climb of dislocations for the normal hardening behaviour and solute drag in the case where a drop of stress is observed in the stress-strain curve.