Pulse current auxiliary bulging and deformation mechanism of AZ31 magnesium alloy

The effects of pulse current on the deformation behavior, dislocation structure, microstructural evolution and cavity morphology of the coarse-grained (25 μm) AZ31 magnesium alloy during gas bulging process were investigated. The tests of pulse current auxiliary bulging (PCAB) showed that the formability of the alloy was improved as the increase in the peak current density. The results of TEM and SEM analysis showed that the dislocation motion was mainly glide, and the dislocation lines were approximate parallel with few dislocation tangles observed. Moreover, a part of cavity tips turned into circular bead by the concentration of the pulse current, and the rounding effect would lead to the relaxing of the high stress concentrated near the cavity tips. These phenomena indicated that the pulse current not only increased the dislocation motion but also restrained the cavity growing during PCAB process. In addition, the asymmetrical contours of the free bulging samples were observed and their forming mechanism was analyzed.