Investigation of interdiffusion and intermetallic compounds in Al–Cu joint produced by continuous drive friction welding

In this paper, the joints between Al and Cu bars were fabricated by continuous drive friction welding. The microstructures and the compositions of the composites were analyzed by SEM, EDS and XRD. The surface temperature was observed using an infrared thermographic camera. The interface temperatures were suggested in the range of 648~723 K at different welding parameters. The interdiffusion between Al and Cu atoms is extraordinarily rapid, as the interdiffusion coefficients could reach 7.8 × 10−12 m2/s. Intermetallic phases Al2Cu and Al4Cu9 were identified in all samples in view of the XRD and EDS analyses. The effective Gibbs free energy change of formation model was proposed to predict the Al–Cu compound formation at solid-state interface, and the calculation combined with kinetic factors showed that Al2Cu (Al side) and Al4Cu9 (Cu side) appeared first.