Rolling of continuously cast Al/Cu composite strips with geometrically designed interfaces

• Applicants: Professor Dr.-Ing. Gerhard Hirt; Professor Dr.-Ing. Wolfram Volk
• Subject Area: Primary Shaping and Reshaping Technology, Additive Manufacturing
• Term: since 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 457434681

The aim of this research project is the development of a method to produce a material composite of aluminum and copper exclusively by a continuous compound casting process with a subsequent rolling process. With this short process route, it would be possible to produce semi-finished composites of aluminum and copper, which are further processed in key technologies such as electromobility, close to final dimensions and at low cost.So far, cold roll cladding has been the most productive process route for the production of this material composite. Before roll cladding, both materials must be cast, rolled and surface treated. This is followed by a heat treatment to increase the bond strength and a further rolling process to achieve the desired thickness of the composite.For the material combination of aluminum and copper, however, this process is not yet possible due to the significant intermetallic phase that arises during casting between the bonding partners. Due to this intermetallic phase, the material composite has a very low bond strength. It can be observed that during subsequent rolling the composite partners shear off each other along the intermetallic phase. Preliminary work suggests that this is due to the shear stresses occurring in the contact plane, which are attributable to the unavoidable difference in strength between the composite partners.Studies have shown that a particularly high surface enlargement is required to crack a significant intermetallic phase and to allow the bonding partners to come into direct contact. At the same time, large normal compressive stresses are required to create a direct bond of high strength between the bonding partners. However, in the rolling of continuously cast Al-Cu composites, the intermetallic phase is so thick that the damaging effect of the shear stresses is always noticeable before the intermetallic phase is cracked wide enough to produce a direct high-strength material bond.Nevertheless in order to produce Al-Cu composites by this promising process route, the present research proposal is intended to investigate how a geometrically distinct interface, created during casting with structured stationary graphite moulds, can prevent the damaging effect of shear stresses. This geometrically distinct interface serves to prevent a relative movement between the composite partners due to the geometrical constraint of its structure and thus to prevent the destructive shear stresses in the composite plane. Thus, a high surface enlargement can be achieved during rolling without the composite partners shearing off each other.

• DFG Programme: Research Grants