Abstract
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.
Highlights
Mitigating climate change with all its consequences requires in comprehensive strategy
The critical impact velocity of Al–Cu for the initiation of bond formation shows a dependence on the intersection of the upper and lower collision angle boundaries, like the similar material configurations
The modified empirical approximation by Wittman can be applied for Al–Cu, whose universal applicability has to be validated for other dissimilar material combinations
Summary
Mitigating climate change with all its consequences requires in comprehensive strategy. A promising, environmentally friendly joining technology is electromagnetic pulse welding (EMPW), which belongs to the group of collision welding processes, such as explosive welding or foil actuator vaporization [1] All of these welding techniques are based on the collision of two joining partners, often referred to as moving flyer and stationary target, at high relative velocity (called impact velocity vimp) and a certain collision angle β [2]. Brittle layers of oxides and other surface contaminations are spalled from the strongly deformed surfaces and form a dispersed cloud of particles (CoP) ahead of the collision front [4] Both phenomena can interact with each other, with the colliding surfaces and with the ambient gas in the welding gap by entrapment and the stored thermal and chemical energy, as discussed in the literature [5,6,7,8,9]. It is challenging to predict the weld formation, especially when dissimilar metals have to be joined
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