Effect of Welding Speed on Metallurgical Characterization of CMT Welding of Dissimilar Aluminium Alloys of AA6061 and AA8011

Dissimilar AA6061 and AA8011 aluminum alloys were subjected to Cold Metal Transfer (CMT) welding using ER4043 (Si-rich) filler wire. The study focused on establishing correlations between the mechanical properties and microstructure of the welded joints. Microstructural analysis unveiled an equiaxed dendritic structure at the weld center and elongated grains at the periphery of the partially molten zone (PMZ). The XRD results indicated the presence of α-Al, Mg₂Si, and Al₁₃Fe₄ intermetallic phases in the PMZs and the weld center. The equiaxed dendrite structure in the WFZ contributed to higher hardness and strength, which can be attributed to the dilution effect and the absence of defects. The interface region on the AA8011 side exhibited enhanced tensile strength and microhardness due to the higher volume of fine secondary phases in the PMZ and finer grains at the WFZ. This comprehensive analysis sheds light on the intricate relationship between mechanical properties and microstructure of the CMT-welded joints, providing valuable insights into the factors influencing the integrity of the welds and interface regions. The maximum tensile strength (97.39 MPa) was observed at a current of 70 A with a welding speed (WS) of 20 mm/s, while the minimum tensile strength (79.84 MPa) was perceived at a WS of 5 mm/s with a current of 50 A.