Joining different metals and minimising negative influences of intermetallic phases

By combining different metals, components that unite the best properties of the materials can be joined. For example, the low weight of aluminum and the high strength of steel combined properly result in a lightweight yet safe car body part.

However, some obstacles have to be overcome when joining different metals. Different thermal conductivity and expansion as well as different strength properties can easily lead to distortion of the component. Different melting points and different metallurgical features carry the risk of intermetallic phase formation which can result in cracking and component failure depending on their severity.

Joining aluminum and steel

The thermal joining of steel and aluminium requires minimising the brittle intermetallic phase or reducing the negative effects of this phase on the joint. If this is successful, the combination of these two metals is highly attractive for the automotive industry. The high strength of steel ensures safety in the event of a crash, the low density of aluminum minimises the weight of the car body and increases the energy efficiency of the vehicle.

In cooperation with our research partner ISF, we have specifically adjusted low-energy, controlled short-arc processes to the demands of the application. In combination with a low-melting zinc-based wire filler material, the brittle intermetallic phase is deposited in a ductile zinc matrix. As a result, high-strength joints can be achieved with low-cost technology.

Joining aluminum and copper

Due to its high electrical conductivity, low cost and low weight, aluminum is increasingly being used as a substitute for copper lines. Nevertheless, most connection elements are still copper-based for functional reasons and require safe electrical and mechanical connection to the aluminum lines.

Intermetallic phases impair the mechanical and electrical properties here as well, which makes the use of fusion welding processes more difficult. Thanks to years of joint research with the ISF,  we have a “toolbox” full of low-heat joining techniques such as resistance welding, friction stir welding or ultrasonic welding. These processes minimise the formation of intermetallic phases and improve the mechanical and electrical reliability of the connections.

Developing material joining concepts

In cooperation with you, we analyse the requirements for the joining process for your dissimilar metal material joint. We then select suitable joining processes, produce prototypes and examine those, if required, for strength, conductivity or aging resistance. In doing so, we constantly optimise the process parameters so that the final result is a component that combines only the best characteristics of the materials.