Friction stir welding (FSW) is a welding process invented and patented in 1991 by Thomas, W.M. et al., at The Weld Institute (TWI), UK. Comprises a extremely simple technique, which consists in joint materials in solid state, independently if similar or dissimilar materials, through higher rates of plastic deformation. This process initially emerged for use in aluminum alloys, and soon attracted interest of other industrial areas, due to its versatility, sustentability and its low energy consumption. Aeronautic and aerospace industries are the areas with huge interest in developing knowledge of this technique, because of the difficulty in joining aluminum alloys of high strength resistance, 2xxx and 7xxx series, by the convencional welding methods, like fusion welding, due to porosity and loss of mechanical properties in the joint. This research investigated the influence of process parameters like rotational speed, welding speed and tilt angle on the results of forging force, torque and temperature, after friction stir welding of similar butt joints of aluminum alloys AA2024-T3 and AA7475-T761. It was found high dependence on rotational speed to guarantee the necessary heat input to plastically deform the material. The tilt angle influenced weld finishing surface and consequent flash. Also investigated the microhardness, residual stress and tensile strength of these joints. Microhardness tests found, in both materials, reduction of values in the heat affected zone, far away from the centre line by 4 to 6 mm. Residual stress results showed a maximum of 81 MPa at advancing side in run 27 of aluminum alloy AA2024-T3, whereas to alloy AA7475-T671 it was found maximum 57 MPa, also in run 27. It was not found evidence of relation between welding speed and longitudinal residual stress. And finally, tensile strength showed approximatelly 84% of efficiency to AA2024-T3, whereas to AA7475-T761 this value was approximatelly 76%.