Cold bonding of aluminium to copper by deformation-enhanced diffusion.

Cold bonding between dissimilar metals and alloys offers several benefits, such as the absence of soft heat-affected zones and thick intermetallic layers with properties that differ from those of the base metals. At room temperature, thermally driven diffusion processes are negligible, but we demonstrate here that mechanically strong bonds are still feasible through high plastic deformation and high strain rates. If the strain rate is high and the temperature is kept low to avoid significant annihilation of vacancies, mechanically strong bonds involving intermetallic compound formation can still form through vacancy-driven diffusion across the contact interface. In the present investigation, two different experimental setups were employed to demonstrate strong bonding between copper and aluminium at room temperature, using phenomenological equations for excess vacancy formation and diffusion to highlight the underlying bonding mechanisms involved. Transmission electron microscopy is used to verify the bonding mechanisms.