Pulse MIG Welding of 6061-T6/A356-T6 Aluminum Alloy Dissimilar T-joint

Dissimilar T-joints between 4-mm-thick wrought 6061-T6 and cast A356-T6 aluminum alloy plates are made with pulse metal inert gas welding (P-MIG) process, and the weld geometry, microstructure and mechanical properties of the joints are investigated. The average tensile load of the joints is 9488 N at travel speed 12 mm/s and welding current 165 A with 6061 aluminum alloy as web plate and A356 aluminum alloy as flange plate. The weld zone (WZ) is composed of dendrite zone and columnar zone, which is wide at bottom of weld making it become a weak zone. Besides, grain boundary (GB) liquation, consisting of GB eutectic and solute-depleted α-Al, occurs in the partially melted zone on 6061 aluminum alloy side. The T-joint with highest tensile load fails at the root of WZ and the flange plate near the weld with different fracture modes.