Formation of Residual Stresses, Strains, and Displacements in Butt Joints of Alloy 1561 During Arc, Plasma, and Hybrid Plasma-Arc Welding

This study investigates the formation of residual stresses, strains, and displacements in 5 mm butt joints of aluminum alloy 1561 produced by metal inert gas (MIG), plasma arc welding (PAW), and hybrid PAW-MIG welding. At the same welding speed and comparable linear heat input, MIG produced the widest weld, whereas PAW produced the narrowest one; hybrid PAW-MIG formed a comparatively narrow weld with nearly equal upper and lower bead dimensions, which makes this process technologically advantageous. The use of a rigid fixture limited longitudinal and transverse shortening to ~ 0.5 mm and caused only slight distortion of the unclamped zone (~ 0.4 mm). Residual transverse stresses did not exceed 25 MPa (< 13 MPa on the weld axis), whereas the average longitudinal residual stress on the weld axis, considering the face and reverse surfaces, was ~ 191 MPa for MIG, ~ 179 MPa for PAW-MIG, and ~ 214 MPa for PAW. Rigid clamping minimized residual stresses and out-of-plane displacements for all methods; the smallest displacements were obtained with PAW, while the most favorable combination of weld geometry and residual stress level was achieved with hybrid PAW-MIG.