Critical Parameters of the Athermal Electroplastic Effect in Metallic Materials

Abstract

Introduction. Plastic deformation and electric current, acting separately, usually have opposite effects on the deformation behavior and flow stresses in electrically conductive materials. In the case of the combined action of plastic deformation and applied electric current, the result is not pre predictable. The study of the synergistic effect of deformation and electric current can be used for metal forming. Aim of the Study. The study is aimed at demonstrating the existence of impulse current threshold parameters at which the athermal electroplastic effect manifests itself in various materials. Materials and Methods. Tensile tests were performed at various current modes, which exclude the increased contribution of the thermal effect to the reduction of flow stresses – current density and duty cycle. The fractographic features of the fracture surface were studied using raster scanning microscopy. There were found the threshold values of current parameters at which stress jumps associated with the electroplastic effect occur. Results. The influence of the density and duty cycle of the impulse current on the manifestation of the electroplastic effect is shown. Both parameters have threshold values, above which the electroplastic effect becomes observable (at density j jкр ) or athermal (at duty cycle Q Qкр). All types of tension are accompanied by a viscous fracture and void formation, which is most intensively formed, when current is injected. Discussion and Conclusion. In alloys with low electrical resistance, the threshold impulse current density corresponding to the occurrence of the electroplastic effect is higher than in alloys with high electrical resistance. Increasing the duty cycle of the impulse current reduces the temperature of the deformed sample that allows considering the electroplastic effect as athermal.

Keywords

• tension
• impulse current
• current density
• duty factor
• fracture surface