Interfacial microstructures and temperatures in aluminium–copper electromagnetic pulse welds

Abstract

Electromagnetic pulse welding can be categorised as a fast, precise, and contactless solid-state joining process. When applied to aluminium and copper, electromagnetic pulse welding opens the possibility of entirely suppressing, or at least minimising, the intermetallic phases of cracking susceptible microstructures. Metallographic examination of aluminium–copper electromagnetic pulse welds revealed that intermetallic-free joints were possible, but rare. When the collision velocity between the workpieces was high (beyond an estimated value of 170 m s−1), a hard copper rich intermetallic phase with the same composition as the equilibrium γ1-(Cu2Al) phase was detected. The presence of both this copper rich intermetallic phase and interfacial voids revealed that melting of the aluminium occurred. A simple analytical model to estimate weld interfacial temperatures was developed and applied to the electromagnetic pulse welding of aluminium with copper. The model not only demonstrated that melting (thus intermetallic phase formation) could have been expected at weld interfaces, but that the model could be extended to estimate appropriate 'intermetallic-free' welding conditions.