Electroplasticity in AZ31B subjected to short-duration high-frequency pulsed current

In this study, the plasticity behavior of an AZ31B magnesium alloy subjected to short-duration (100 μs), high-frequency (120-800 Hz) pulsed current was investigated using tensile tests. The key finding is that the effect of pulsed current on plastic deformation goes beyond the Joule heating effect. In our experiments, the frequency was adjusted to maintain a constant effective current density and, thus, the same Joule heating effect. A comparison with continuous current having the same Joule heating effect was made as well. It was observed that when the peak current density is higher than a critical value, a higher peak current density will yield a more significant reduction in flow stress even though the thermal heating effect is the same. This critical current density decreases with the increase in the effective current density. Pulsed current with a higher peak current density can more effectively reduce the dislocation density through electric-induced annealing, induce more severe grain rotation, and, thus, lower the resistance for dislocations to pass through barriers like grain boundaries, resulting in a more significant flow stress reduction. X-ray diffraction characterizations were also conducted for the deformed specimen to show that a higher peak current density induces more severe grain rotation and, thus, more effectively decreases dislocation density.