Characterization of different Al-to-steel dissimilar welds using an innovative FSW-based process

The innovative friction melt bonding process to join dissimilar materials in lap-joint configuration has been applied to weld aluminium to steel in lap-joint configuration. In this process, a flat cylindrical tool is pressed against a top sheet of steel. The frictional heat generated is large enough to be transmitted through the steel to an aluminium sheet placed below and melt it at the interface. This allows controlling the formation of Fe/Al intermetallics that are responsible for the bonding. Several welds at different advancing speeds of the tool have been carried out using Ultra-low-carbon (ULC)and dual-phase (DP) steels and 1050, 2024, 6061 Al alloys. The microstructure was observed and the thickness of the intermetallic was measured as thin as 2-3 µm at higher advancing speeds. Hardness measurements were performed to assess the different affected zones as well as lap-shear tests to measure the strength of the bonding.