摘要：The present study focuses on the effect of postweldingheat treatments on mechanicalproperties of double-lap Friction Stir Welded(FSW) joints in 2024T3 and 7075T6aluminium alloys. Heat treatments wereperformed at aging and solutiontemperatures. Micro-hardness profilesmeasured on transversal sections of postweldedheat treated joints reveal conditions(temperature and time) of hardnesshomogeneity at top, bottom and centralnugget zone along the whole measuredprofile. When hardness homogeneity isreached, fracture occurs in the nugget. Thedouble lap FSW joints after post-welding heattreatments at low temperatures (200° and300°C) have tensile properties comparablewith the as-FSW joint and fracture occurs in7075T6 Base Material. At highertemperatures, fracture strain is almost 50% ofjoints deformed after heat treatment at lowertemperature and failure occurs inside the stirzone. Polarized Optical Microscopy (POM)and Scanning Electron Microscopy (SEM)analysis reveal a progressive change in grainsize and morphology in high temperaturepost-welding heat treated joints, leading toAbnormal Grain Growth in the stir zone.
