Microfriction welding has been used for joining aluminium to a variety of ceramics for heat extraction or electrical connections. In most applications the ceramic is held stationary, while the softer metal (i.e. aluminium) is rotated and brought into contact. Friction between the components generates heat, which breaks up surface contaminants and increases the plasticity of the metal. After a pre-set time, the rotation is halted, and force is applied to form the weld. Friction welds are characterised by a distinctive flash or collar of metal that is expelled from the ceramic-metal interface during both rotation and forging.
Friction welds can be produced successfully between aluminium rod and a range of ceramics, such as Al2O3, AlN and SiC. Examination of bonds has shown no evidence of chemical reaction or diffusion at the ceramic-metal interface: mechanical keying appears to be a major contributor to bond strength.