Investigation on processing characteristics and action mechanism of the electro-plastic incremental forming for AZ31B magnesium alloy sheet metal

The electro-plastic incremental forming (EPIF) has been demonstrated to be an effective approach for processing the difficult-to-form materials. In this paper, the EPIF experiments of AZ31B magnesium alloy were carried out on a self-designed experimental platform for incremental forming, and then, the forming temperature, forming force, and strain state in the forming process were researched by the experimental investigation and theoretical analysis. It is found that the duration of high temperature for the fixed point in workpiece is very short. The higher electropulse value can cause a higher temperature-rise rate, and the maximum forming temperature can reach over 350 °C at 80 V/400 Hz, while the influence of tool diameter and forming angle on it is negative, and the feed rate and step size have nothing to do with it. The research results of forming force show that the vertical force can increase first, and then, the decreasing trend emerges in the later stage owing to the electro-plastic effect. The horizontal force of tool is generated only in the tangential direction of tool advance instead of radial direction. Furthermore, the electropulse value, step size, and forming angle have a significant effect on vertical force, but the tool diameter does not. The overall vertical force is negatively correlated with the electropulse value, and the minimum vertical force can be reduced to below 400 N at 80 V/400 Hz, while it is positively correlated with the feed rate, step size, tool diameter, and forming angle. Finally, the deformation mechanism of sheet metal in incremental forming was verified by the microstructure study, that is, the shear deformation in the thickness direction of the sheet.