COMPRESSION CREEP OF COPPER UNDER PULSED ELECTRIC CURRENT STUDIED BY A SPARK PLASMA SINTERING (SPS) APPARATUS

The spark plasma sintering (SPS) apparatus, typically used for powder consolidation, keeps growing in popularity due to its excellent sintering capabilities. It utilizes simultaneous application of uniaxial pressure and elevated temperature, generated by a high current flow that passes through graphite tooling. In principle, the SPS apparatus is a high-temperature dilatometer and we have recently demonstrated that it be applied as a creep testing device. Moreover, one can employ two different testing configurations for conductive materials, which determines whether the sample is isolated from the current or not. This allows to study the effect of an electric current passing through the sample on creep behavior and electro-plastic deformation (EPD) of conductive materials.
In the present study, EPD during creep of pure copper under influence of a pulsed electric current (density of ~6-7 A/mm²) was investigated in the 400-600°C temperature range. Experimental results have clearly shown that the electric current significantly enhanced plastic deformation and creep rate. Furthermore, the apparent activation energy for creep under the influence of the electric current (66 kJ/mol) was remarkably lower than that for creep without the current (110 kJ/mol). The nature of this electro-plasticity is attributed to the effect of the electric current on dislocation mobility, by affecting the thermally-activated process which in turn increases the effective stress or temperature. Optical and TEM analysis of deformed samples showed no distinct evidence that the electric current affects the microstructure.