Effect of Severe Prior Deformation on Electrical-Assisted Compression of Copper Specimens

In Electrical-Assisted Forming (EAF), current is passed through the material during the deformation process, which results in a decrease in the required flow stress for the material. While resistive heating occurs, the flow stress reductions are beyond what can be explained by temperature effects alone. Hypotheses for this effect relate to the current affecting dislocation generation and aiding dislocation motion through the lattice structure. If the latter was the case, then materials with higher dislocation densities from severe deformation should have more pronounced benefits from EAF. In this research, Equal Channel Angular Extrusion (ECAE) was used to induce severe plastic deformation into the material. Subsequent EAF compression experiments with the ECAE specimens and as-received material with comparable grain sizes were conducted. As expected, the EAF process reduced the flow stress value substantially more, e.g., 224MPa versus 115MPa at a strain of 0.8 for the ECAE specimens compared to the as-received specimens respectively. These flow stress reductions were from a case with no current applied to a case where an initial current density of 250A/mm² was applied. EAF may particularly be beneficial at the microscale to address size effects as the current required to achieve an elevated current density is more viable.