Friction stir welding (FSW) process is widely used for joining of similar and dissimilar, ferrous and non-ferrous metals in automobile, aerospace, and defense industries. The selection of optimum process and tool parameters for a given workpiece material and thickness is essential to generate adequate heat and material flow around the tool-pin and get a defect-free weld. The experimental approach in designing optimum parameters is a tedious, time-consuming, and expensive, and therefore, the simulation-based approach would be cost-effective and also provides a comprehensive data in real-time. A 3-D coupled thermomechanical model is developed in COMSOL Multiphysics software and studied the effect of welding speeds (200–600 mm/min) on thermal histories, workpiece material deformation, von Mises stresses, equivalent plastic strains, and weld zones in butt welding of Al-Cu binary alloy (2219-T87) plates at high welding (traverse) speeds. The yield stress-based frictional heat source model and temperature-dependent thermophysical and mechanical properties of AA2219-T87 are used. A conical tool-pin (8 and 5.5 mm as pin diameters, 5.5 mm pin height, 21 mm tool shoulder diameter) with 750 rpm and 25 kN load is used for 6 mm thick plates. The authors proposed a range of temperatures for FSW zones of AA2219-T87, and found a good agreement between the predicted and experimental zones with material bulge at the tool shoulder edge, which decreases with an increase in welding speed.