Deformation mechanisms of AZ31 Mg alloy sheet assisted by electrical pulse- ultrasonic composite energy field

Ultrasonic vibration and pulsed current can achieve energy concentration and effectively improve the forming ability of Magnesium alloy sheets. The uniaxial tensile tests of AZ31B sheets assisted by electric pulse, ultrasonic and electric pulse-ultrasonic composite energy fields were carried out, respectively. The influence of the effective current density and duration of the electric pulse on the softening, hardening and residual effects in the deformation process caused by the coupling action were explored. The electric pulse suppresses the promoting effect of ultrasonic vibration on twinning and together with ultrasonic vibration promotes dislocation slip to coordinate deformation. The composite energy field can thus further reduce the deformation resistance. The softening, secondary hardening and residual softening phenomena caused by the electric pulse-ultrasonic composite energy field become more and more significant with the prolongation of duration. When the ultrasonic field with a frequency of 21 kHz and an amplitude of 10 μm is combined with a frequency of 600 Hz and the effective current density increases from 0 to 30 A/mm², the influence on the softening and secondary hardening process exhibits an initial increase followed by a decrease as the current density increases, while the influence on the residual softening shows the opposite trend.