A study on the metallurgical and mechanical properties of a GMAW-welded Al-Mg alloy with different plate thicknesses

Thick plate of 5083 aluminum alloy with 8 mm, 20 mm and 30 mm thicknesses are joined by double-side GMAW method. The influence of plate thickness on the welding stability, weld bead formation, porosity formation, microstructure and mechanical properties are investigated and compared. The results reveal that, with the increase of plate thickness, the stability of GMAW process, weld bead formation of the welded joints and the results of bending tests are similar. In larger plate thickness, more welding passes resulting in more source of hydrogen, larger specific surface area caused by thinner droplet, and the high solidification rate synergistically contribute to easier formation of porosity. With the increasing of plate thickness, higher peak temperatures of thermal cycles can lead to larger grain size. Besides, lower density of second-phase particles and more porosity of welded joint in larger plate thickness result in lower strength.