摘要：The present study focuses on the effect of postwelding heat treatments on mechanical properties of double-lap Friction Stir Welded (FSW) joints in 2024T3 and 7075T6 aluminium alloys. Heat treatments were performed at aging and solution temperatures. Micro-hardness profiles measured on transversal sections of postwelded heat treated joints reveal conditions (temperature and time) of hardness homogeneity at top, bottom and central nugget zone along the whole measured profile. When hardness homogeneity is reached, fracture occurs in the nugget. The double lap FSW joints after post-welding heat treatments at low temperatures (200° and 300°C) have tensile properties comparable with the as-FSW joint and fracture occurs in 7075T6 Base Material. At higher temperatures, fracture strain is almost 50% of joints deformed after heat treatment at lower temperature and failure occurs inside the stir zone. Polarized Optical Microscopy (POM) and Scanning Electron Microscopy (SEM) analysis reveal a progressive change in grain size and morphology in high temperature post-welding heat treated joints, leading to Abnormal Grain Growth in the stir zone.
