Diffusion-enhancement during Electrically Assisted Solid-state Bulk Joining of Copper C11000 and Al-Mg-Si Aluminum Alloys

The athermal effect of electric current on diffusion enhancement during electrically assisted solid-state bulk joining of a C11000 copper alloy and an Al-Mg-Si alloy (AA6061-T6) is investigated. A primary electric current with various current densities is applied to the assembly of cylindrical specimens (along the axial direction) under a fixed plastic deformation condition, followed by repeated pulsed currents. The primary current is designed to keep the thermal input constant while varying the athermal contribution by changing the current density and current duration. Therefore, the joining temperature and the total energy, defined as the sum of mechanical and electrical energy, remain nearly identical for all joining conditions, enabling a clear separation of thermal and athermal effects. Microstructural analysis shows that increasing current density significantly enhances interfacial diffusion and alters the microstructural evolution at the joint interface. The athermal effect on diffusion kinetics is quantitatively evaluated using effective activation energy and effective temperature.

Keywords: solid-state bulk joining; current density; athermal effect; diffusion kinetics