Cavitation Behavior in Superplastic AZ31 Magnesium Alloy During Pulse Current Auxiliary Gas Blow Forming

During the gas blow forming of AZ31 magnesium alloy, the heavy pulse current was applied. The effects of pulse current on the cavitation during superplastic forming were examined. Scanning electronic microscopy (SEM) was employed to observe the cavities and topography of the forming samples. Theoretical analysis and experimental results show that the pulse current flowing through the cavity tip will form a local high-temperature zone and local compressive stress area near the vicinity. It is helpful to heal the cavity and avoid the further growth; at the same time, the non-thermal effect of pulse current will also affect the cavity nucleation and growth, thereby changing the morphology and distribution of cavities. It delayed the appearing of large size cavity to some extent, avoiding the material premature fracture and helping to improve the forming limit of the material during the superplastic deformation.