Microstructure and mechanical properties of aluminium/steel dissimilar weldments: effect of heat input

Lap joints of aluminium alloy A6061-T6 and galvanised steel DP800 were produced by an advanced gas metal arc welding process with AlSi3Mn filler. Four heat inputs designated as A (110 J mm(-1)), B (120 J mm(-1)), C (130 J mm(-1)) and D (140 J mm(-1)) were used during the process and the joints made were subjected to analysis of the microstructures, mechanical properties, residual stresses and corrosion behaviour. Microstructural analysis shows the formation and variation of Fe-Al intermetallic (IM) layer. It is also found that the joints made using the heat input of 120 J mm(-1) exhibited highest tensile strength and better corrosion resistance. Electron microscopy and X-ray diffraction analysis revealed the presence of different IM phases with other strengthening precipitates.