Tensile fracture behavior in CO2 laser beam welds of 7075-T6 aluminum alloy

CO2 laser beam (LB) welding is conducted on 7075-T6 aluminum alloy sheets at two different welding speeds and compared with gas tungsten arc (GTA) welding. The mechanical and microstructural characteristics of the welds are evaluated using tensile tests, hardness tests, optical microscopy and energy dispersive X-ray spectroscopy (EDS). Results indicate that both the hardness and tensile strength of LB welds are higher than those of GTA welds. It is shown that the hardness value of the softened region in LB welds is in the fusion zone (FZ), whereas that in the heat affected zone (HAZ) of the GTA weld. Tensile strengths of LB welds after the post-weld artificial aging treatment at 120 °C for 26 h are improved but cannot be equivalent to those of base metal because the softened FZ of the LB weld is not completely recovered after post-weld artificial treatment.