The joining of AA6063 plates of 12 mm thickness was carried out by friction stir welding (FSW) technique. In the present investigation, the AA6063 was welded with the tool rotational speed of 470, 590,740 and 900 RPM and at a welding traverse speed of 16, 31.5, and 50 mm/min. Charpy V- notch impact test was carried out to analyze the impact strength of the welded specimen at a room temperature, -30ᵒ, and -60ᵒ. With increasing the tool rotational speed impact energy behavior shows a substantial change in mechanical properties. The microstructure was investigated and the grain size was measured to get the minimum grain size.