Abstract
The joining of dissimilar metals is an important issue in modern lightweight design. Friction Stir Welding (FSW) is suitable for this task since the solidus temperature is usually not exceeded during the process. As a consequence, dissimilar joints can be produced with a minimum of deteriorating intermetallic phases. The latest studies showed the formation of intermetallic layers at the bonding interface with no significant negative influence on the seam quality. In this study, those intermetallic nanolayers at the interface of aluminium / copper lap joints were analysed. For the experiments, the commercially pure alloys EN AW-1050 and CW008A were chosen. The process temperature changed with respect to the parameter setup and was measured at different locations of the seam. The intermetallic layers at the interface were analysed by scanning electron microscopy (SEM) and scanning transmission electron microscopy (STEM). The experiments show that the thickness of the interlayer clearly correlates with the process temperature using an Arrhenius equation. It is supposed, that the rotating probe removes the oxide layers of the metal surfaces and a metallic bonding between the Al- and the Cu-phase is formed. Due to the elevated temperature after the probe has passed, the intermetallic layer has emerged by interdiffusion.
Highlights
The use of materials adapted to the locally specified requirements of structures is one of the most promising solutions in modern lightweight design to reach higher efficiencies in terms of energy, mass and cost reduction
The mean temperature in both materials increased with an increasing rotational speed and saturated at a temperature of about 390 °C
The difference between the minimum and the maximum peak temperatures in the aluminium sheet significantly rises for rotational speeds n > 1300 min−1
Summary
The use of materials adapted to the locally specified requirements of structures (e.g. load capability, thermal/electrical conductivity) is one of the most promising solutions in modern lightweight design to reach higher efficiencies in terms of energy, mass and cost reduction. This results in the necessity of combining dissimilar materials. The thermal and physical properties of these material combinations are often very different or even competing. The joining of dissimilar materials remains challenging for traditional fusion welding technologies. Innovative solid state welding technologies, such as Friction Stir Welding (FSW), are suitable for this task.
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