The paper deals with welding of aluminum alloys using Friction Stir Welding technology. This represents one of the solid-state welding technologies in which the base materials are not melted. This welding method provides new possibilities for the use of special and hybrid manufacturing technologies. The article first presents an overview and the current progress in the Friction Stir Welding technology. Further, the key attributes of the technology are stated, focusing on the individual weld microstructure zones and their characteristics. Subsequently, a computer simulation of the FSW thermal cycle of an aluminum alloy specimen was designed in the program Ansys; the simulation provides the distribution of the temperature fields within the welded material. The simulated temperature fields are compared with a real weld joint, and possible defects are pointed out. Finally, the results of the computer simulation and of the visual analysis of the real weld joint are summarized and discussed.Friction Stir Welding FSW Aluminum Aluminum alloys Simulation