Influence of Surface Preparation on the Interface of Al-Cu Joints Produced by Magnetic Pulse Welding

Adhesion of thin metallic layers on Au surfaces

We carried out first-principles density-functional theory calculations to study the work of separation for five different metal-metal interfaces, each of them comprising thin layers of selected metals (Cr, W, Ta, Al or Ti) lying on top of Au surfaces. We found that the highest work of separation is obtained for one-atom-thick layers. Increasing the number of atomic layers leads the work of separation to oscillate with the thickness, and ultimately tend to a limiting value for a large number of layers. Interestingly, for most cases the lowest work of separation is obtained for two-atom layers. We find that this behaviour is mirrored by the quantity of charge transferred between the two metals on the one hand, and their spatial distance on the other.

The Energy Balance in Aluminum–Copper High-Speed Collision Welding

Collision welding is a joining technology that is based on the high-speed collision and the resulting plastic deformation of at least one joining partner. The ability to form a high-strength substance-to-substance bond between joining partners of dissimilar metals allows us to design a new generation of joints. However, the occurrence of process-specific phenomena during the high-speed collision, such as a so-called jet or wave formation in the interface, complicates the prediction of bond formation and the resulting bond properties. In this paper, the collision welding of aluminum and copper was investigated at the lower limits of the process. The experiments were performed on a model test rig and observed by high-speed imaging to determine the welding window, which was compared to the ones of similar material parings from former investigation. This allowed to deepen the understanding of the decisive mechanisms at the welding window boundaries. Furthermore, an optical and a scanning electron microscope with energy dispersive X-ray analysis were used to analyze the weld interface. The results showed the important and to date neglected role of the jet and/or the cloud of particles to extract energy from the collision zone, allowing bond formation without melting and intermetallic phases.

Effect of Different Filler Wires on Mechanical Property and Conductivity of Aluminum-Copper Joints

The 1060 aluminum and T2 copper were joined by the pulsed double electrode gas metal arc welding (DE-GMAW) brazing method by using four types of filler wires, namely pure aluminum (Al) ER1100, aluminum-magnesium (Al–Mg) ER5356, aluminum-silicon (Al–Si) ER4043, and Al–Si ER4047, respectively. The effects of different types of filler wires on intermetallic compounds, microhardness tensile strength, and conductivity of joints were investigated. The results showed that a lot of brittle intermetallic compounds laying in the copper side brazing interface zone were generated using pure Al, Al–Mg, and Al–Si filler wires, which caused the change of microhardness, tensile strength, and the conductivity of joints. Meanwhile, with the increase in Si elements contents for Al–Sifiller wires, the thickness of the intermetallic compound layers decreased obviously, which was only up to 3 µm and the conductivity of the joints decreased. In addition, the microhardness, tensile strength, and the conductivity of the joints, when using Al–Sifiller wires, was higher than that using pure Al and Al–Mg filler wires. Hence, in comparison to the pure filler wires and Al–Mg filler wires, the Al–Si filler wires were more suitable for Al–Cu joints by DE-GMAW as Si element content was lower.