Interface Characterization by Nanoindentation and EBSD of Cu/Cu and Al/Cu Joints Produced by Magnetic Pulse Welding (MPW)

Magnetic Pulse Welding (MPW) is a high-velocity impact welding technique that allows the joining of dissimilar materials such as aluminium and copper. Welding should be produced under the appropriate conditions: impact velocity (200–500 m.s−1) and collision angle (10–30°). The formation mechanisms leading to the welding creation are not very clear. This work investigates the microstructure and hardness at the interface to understand these mechanisms. Al/Cu and Cu/Cu samples were formed with identical process parameters. They were first compared to the literature using Vickers microhardness. Obtained results are standard and correspond to previous studies. In a second step, a detailed characterization of the interface using nanoindentation and electron back-scattered diffraction (EBSD) methods is done. Different behaviors were found at the interface between Al/Cu and Cu/Cu. Al/Cu exhibited a thin layer of intermetallic compounds (IMC), increasing the hardness at the interface. This layer was composed of Al2Cu and Al4Cu9 compounds, as demonstrated by Energy Dispersive Spectroscopy (EDS) and X-ray Diffraction (XRD). Cu/Cu presented a dissimilar behavior at the interface. The flyer sheet shows an increase in hardness due to grains deformation and distortion. While, the base sheet manifested a decrease in hardness caused by dynamic recovery or recrystallization at the interface. In both cases, the samples were deformed and hardened due to the plastic deformation induced during impact. These results are complementary to previous studies. They provide new insights that could be used to improve our understanding of the mechanisms behind such high-velocity impact welding.