Microstructure and mechanical properties upon electrically assisted deformation of magnesium alloys
Despite the good combination of strength and very low density, the low ductility of magnesium and most of its alloys imposed by the hcp lattice has so far limited their use in engineering applications. The formability of magnesium alloys can be increased by employing the electro-plastic effect. Moreover, electro-plastic forming may be much more energy efficient than conventional hot forming. In order to be able to develop a suitable electrically-assisted forming technology, the microstructural mechanisms that trigger material softening upon application of high current densities must be understood. In the presented study, the influence of short electric pulses (duration of 1-2 ms) with a current density of 2,000 to 8,000 A/mm2 on the microstructural evolution and the resulting mechanical properties were investigated for various magnesium alloys.
Different current directions were employed to evaluate the effect of the orientation of the applied electric current with respect to the mechanical load on the materials’ response. In addition, the influence of grain size of the alloy on the magnitude of the electro-plastic effect was determined. It will be demonstrated that the mechanical properties of coarse-grained alloys are more strongly influenced by the current pulses than those of fine-grained ones. Moreover, the current pulses applied parallel to the mechanical load showed a stronger softening of the material than current application perpendicular to the mechanical load. The results will be analysed in terms of the governing microstructural mechanisms, and the ramifications will be discussed with respect to the envisaged applications.