Effect of Strain Rate on the Mechanical Behavior of Al-Mg Alloy Under a Pulsed Electric Current

Electrically assisted forming brings many advantages to the forming processes of metal alloys through microstructure modification by a flowing current. However, the influence of strain rate on these changes and the real value of the stress-drop are not yet specified. In this study, the effect of strain rate on flow stress, material plasticity and, microstructure was analysed for the electrically assisted tension of the 5754-H111 aluminium alloy. Three different strain rates (0.0025, 0.01, and 0.04 s⁻¹) were applied under a pulsed electric current tension. The study showed that at decreasing strain rate, an increase in engineering strain is observed. This effect was explained by the periodic strain-hardening and annealing of the sample under a pulsed electric current. The study also showed the possibility of determining the real value of stress-drop, which occurred when a pulsed current was applied during tension. Finally, applying the current pulses led to a meaningful increase in the material plasticity. Transmission electron microscopy and electron backscatter diffraction were used to identify the microstructural changes. It was shown applying pulsed current allowed a change of the dislocation pattern and its annihilation, resulting from the dynamic recovery process.