Nugget formation analysis of Al/Steel clinch-resistance hybrid spot welding

A clinch-resistance hybrid spot welding method was presented to join Al and steel. The nugget formation was analysed via microstructure observation and numerical simulation. A cup section nugget was formed, and the melting zone was mainly formed at the nugget edge with a thin layer of interfacial intermetallic compounds. Numerical simulation results showed that peak contact stress on the steel/Al contact surface was located at the connection between the punch tip and die tips. Aa remarkable amount of heat was first generated at the nugget edge and then transferred to the centre, but the temperature at the edge was relatively low. Compared with traditional spot welding, a unique distribution of heat occurred during the welding process.