Abstract—Friction-stir welding has received a huge interest in the last few years. The many advantages of this promising process have led researchers to present different theoretical and experimental explanation of the process. The way to quantitatively and qualitatively control the different parameters of the friction-stir welding process has not been paved. In this study, a refined energy- based model that estimates the energy generated due to friction and plastic deformation is presented. The effect of the plastic deformation at low energy levels is significant and hence a scale factor is introduced to control its effect. The predicted heat energy and the obtained maximum temperature using our model are compared to the theoretical and experimental results available in the literature and a good agreement is obtained. The model is applied to AA6000 and AA7000 series. Keywords—Friction-stir welding, Energy, Aluminum Alloys. I. INTRODUCTION HE energy required to bond two components by welding is usually provided by direct heat. The two common sources of direct heat are those derived from either a chemical reaction or electrical energy. The exception includes explosive bonding, which uses the kinetic energy released from the impact of a moving object with a stationary target and friction-stir welding, which combines frictional heating at the interface with the localized plastic deformation within the material. Friction-stir welding (FSW) is a solid-state joining process that enables welding hard-to-wild metals such as high-strength aluminum alloys. Friction-stir welding was developed and patented by The Welding Institute (TWI) in 1991 [1]. Since then the research efforts to understand the micro and macromechanics of the process are continuous. During FSW, no melting point occurs, and as a result the process is performed at much lower temperatures than conventional welding processes. This has a direct impact on the safe application of the FSW to the environment. Among the advantages of the FSW are [2] • Low distortion, even in long welds • Excellent mechanical properties as proven by fatigue, tensile and bend tests • No arc Samir Emam is with the Department of Mechanical Engineering, United Arab Emirates University, P.O. Box 17555, Al Ain, UAE; e-mail: semam@ uaeu.ac.ae. Aly El Domiaty, Department of Mechanical Engineering, Suez Canal University, Port Said, Egypt. • No fume • No porosity • No spatter • Low shrinkage • Energy efficient • Non-consumable tool; one tool can typically be used for up to 1000m of weld length in 6000 series aluminum alloys • No filler wire • No gas shielding for welding aluminum • No grinding, brushing or pickling required in mass production • Can weld aluminum and copper of more than 50mm thickness in one pass. However, as of the present time, there are some limitations, which include • Workpieces must be rigidly clamped • Backing bar required, when self-reacting tool or directly opposed tools are not available. • Keyhole at the end of each weld. • Cannot make joints which require metal deposition (e.g. fillet welds) Friction-stir welding is carried out using a rotating tool that is attached to a shoulder piece and the whole unit is translating over the line of welding. The rotation and translation of the pin within and on top of the line of welding generates heat, which is used to weld the workpieces. Heat is generated due to plastic deformation of the workpiece and the effect of the friction between the surfaces of the tool and the workpiece [3, 4]. Figure 1 is a schematic of the friction stir welding process. According to most of the literature, the weld zone around the tool is divided into four regions: unaffected or parent metal, heat affected zone (HAZ), thermo-mechanically affected zone (TMAZ), and weld nugget. The unaffected material is remote from the weld, which has not experienced deformation or it may have healed after being experienced a thermal cycle. The heat affected zone (HAZ), which was previously referred to as thermally affected zone, is in the neighborhood of the weld center and its microstructure and mechanical properties have been modifies as a result of experiencing a thermal cycle. This zone does not associate a plastic deformation. Thermo-mechanically affected zone (TMAZ) is plastically deformed due to the friction-stir welding tool and its microstructure is modified due to the generated heat. Finally, the weld-nugget zone is the A Refined Energy-Based Model for Friction-Stir Welding Samir A. Emam and Ali El Domiaty T 101