Influence of heat cycle and degree of dilution in electron beam welding on the properties and the long-time behaviour of aluminium copper dissimilar material joints in current-carrying parts

• Applicant: Professor Dr.-Ing. Uwe Reisgen
• Subject Area: Production Automation and Assembly Technology
• Term: from 2017 to 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 342185193

A great potential for light-weight construction, above all in the field of electro-mobility, lies in the substitution of copper by aluminium. It is, moreover, possible to apply aluminium as a conductor and copper as a contact material (firmly bonded joining). The state of the art, so far, has put the focus only on the identification of the crack-sensitive intermetallic phase (IPS). Besides the IPS, the larger part of the joint consists of an Al-Cu mixed crystal which is similar to an EN-AW-2xxx alloy, as suggested by the tests which have been carried out. A verification of this allows the transfer of the known electric and mechanical properties of 2xxx alloys to the dissimilar material joint. It is expected that the mixed crystal formation leads to the increase of strength but, at the sime time, to a reduction of the electric conductivity. External influential factors, such as temperature, currentfeed and time bring about the change of the joining zone structure by diffusion and electro-migration. Moreover, a temporal change of the technological properties (increase of the electric resistance, reduction of strength) of the dissimilar material joint will occur. Findings about this behaviour will allow to draw conclusions about the expected lifetime of the joints.The aim of the research project is to achieve overall comprehension about develoment, structure and temporal changes (by electric operation) of the material-binding aluminium / copper dissimilar material joints. The exceptionally fast and precise beam manipulation of electron beam welding allows to achieve specific temperature-time sequences and dilution degrees. This way, the IPS shall be influenced during the welding process with regard to compositon and formation of unrequired phases (for example with higher ductility or electric conductivity). An attempt will be made to set the optimum for the expected service life between the opposedparameters (strength and electric conductivity).

• DFG Programme: Research Grants