Respective roles of the thermal and electromigration effect in AZ31 Mg alloy during low-frequency electropulsing tension

The low-frequency electropulsing tension (ET) tests of AZ31 Mg alloy were carried out with/without forced air-cooling (FAC), which were denoted as FAC-ET and ET, respectively. The roles of the thermal and electromigration effect on the microstructure evolution and mechanical properties were elucidated. Tension test without electropulsing (Non-ET) was performed and the results were compared with that of the ET and FAC-ET samples. Our results indicate that the electropulsing is beneficial for the elongation, but weakens the flow stress due to the enhanced dynamic recrystallization. Both the thermal and electromigration effect can promote the plasticity, but the thermal effect is the main factor that causes the decrease of tensile strength. Moreover, the ET sample shows a higher recrystallized fraction and larger elongation compared with the FAC-ET sample although their recrystallized grains possess similar grain size. Calculation and experimental results support that the thermal and electromigration effect both contribute to the increased recrystallized degree. The thermal effect dominates the nucleation of recrystallization while the electromigration effect is in charge of the growth of recrystallized grain. •The ET sample shows more recrystallized grains and lower GND density.•The FAC-ET sample shows a lower DRX degree and weaker electroplasticity.•The thermal effect dominates the nucleation of recrystallization.•The electromigration effect is in charge of the growth of recrystallized grain.•The mechanism of DRX under low and high frequency pulsed current is different.