Electroplastic effect in the process of electromagnetic forming

Abstract

Using the example of a riveted aluminum alloy AMg-2, a  significant increase in technological plasticity during deformation by a magnetic pulse is shown in comparison with a mechanical flexible one. The first microcracks on the stretched surface appeared only after 37% deformation, whereas in the case of mechanical bending they appeared already at 7.6%. The duration of the active part of the pulse deforming the workpiece is less than 0.1 ms, the rate of relative deformation of the workpiece is ε ≈ 5⋅103 s–1. As a result of this treatment, microhardness increased from 94 to 110 HV, the appearance of specific residual stresses and a decrease in grain size in the surface layer. The increase in plasticity is explained by the electroplastic effect caused by a high-density current pulse induced in the workpiece by the inductor field. At the same time, the surface temperature of the workpiece did not exceed 80 °C, which excludes thermal restructuring of the alloy structure, given the brevity of events. The repeated action of electromagnetic pulses with intermediate cooling reduces the level of residual stresses, which can also be considered an effect of electroplasticity. The  obtained patterns can be useful for deformation processing of workpieces made of pre-hardened materials with limited ductility.