The aim of the present research was to study the effect of friction stir welding parameters such as ( tool rotation and tool travel speeds) on the impact energy of (6.1 mm) thick weldments of aluminum alloys (2024-T351,7075-T651).Which are used in aircraft industries andare poorly weldable by fusion welding such as (TIG,MIG and Laser) welding .Friction stir welding welds were carried out on a traditional milling machine .Tow tool rotation speeds (900 and 1120 rpm) and three travelspeeds (28,40 and 56 mm/min) were selected for the friction stir welding of each alloy. The resistance of the weldments has been investigated using the impact test with standard V-notched specimens at room temperature.Finally a comparison has been made between welds impact energy and base metal impact energy. Ithas been observed that the impact energy increased at the friction stir welding of both alloyscompared with the base metal for most cases. The impact energy of the (2024-T351) Al alloy reduced with increasing the rotation speed of the tool at the same travel speed , while rotation and travel speeds have a little effect on the impact value of (7075-T651) Alalloy and the results are very close to each other.
Key words: Friction stir welding, high strength aluminum alloys, impact energy.