Joining of the aluminium alloy sheets wtih friction stir spot welding and investigation of their strength properties

Electric resistance welding is commonly used in automotive industry but it has negative effects on metallurgical and mechanical properties of materials and that?s why friction stir spot welding (FSSW) is choosen in this study as an alternative method for welding, instead of electric resistance welding at the process of joining the sheets of Al 6061 and Al 7075. For invesigation, three specimen combination were made up from the AA 6061 and AA7075 aluminium alloy sheets which have 3 mm thickness. Tool rotational speed and process time were constant and three different tool geometries were variable parameters for each specimen group. The tests of tensile strength, and micro hardness were used to find out the mechanical properties of friction stir spot welds, and also parent metal (PM), thermo mechanical affected zone (TMAZ) and heat affected zone (HAZ) were observed by using microstructure and scanning electron microscope (SEM ) pictures of the cross sections. Best mechanical and metallurgical results were gained from the specimens which were joined with friction stir spot welding (FSSW) by using cylindirical tool geometry.