Effect of GMAW Process Parameters and Filler Alloys on Solidification Cracking and Mechanical Behavior of AA6061 and AA7075 Aluminum Alloys

This study investigates the effect of Gas Metal Arc Welding (GMAW) parameters on solidification cracking and mechanical behavior of AA6061 and AA7075 aluminum alloys, which are widely used in automotive, aerospace, and battery-related applications due to their low density, corrosion resistance, and high specific strength. The influence of filler metals, ER4043 and ER5356, welding speed, wire feed speed, and calculated heat input was evaluated using the Circular Patch Test (CPT). Surface and internal cracking were examined by X-ray inspection, while microstructural evolution, phase formation, hardness, tensile behavior, and local strain distribution were analyzed using optical microscopy, SEM/EDS, XRD, microhardness testing, micro-tensile testing, and Digital Image Correlation (DIC). The results show that cracking susceptibility depends on the combined effects of welding speed, heat input, filler-metal chemistry, and dilution. The observed cracking behavior is associated with local compositional variations, weld defects, and the formation of low-melting/eutectic or secondary constituents within the fusion zone, rather than being attributed to a single factor. ER5356 showed favorable cracking resistance for AA7075 under the selected conditions, while ER4043 generally improved cracking resistance for AA6061. The mechanical response and fracture behavior were also influenced by filler composition and local weld microstructure. These findings provide useful guidance for selecting welding parameters and filler metals to improve weld quality and reduce solidification cracking in AA6061 and AA7075 aluminum alloys.