Friction stir welding (FSW) has been used to join metallic and non-metallic materials without melting the base metal. this process employs a non-consumable rotary welding tool consist of a shoulder and a pin. the friction between the tool and the work piece generates heat which is coupled with the axial pressure on the tool contribute in the production of a permanent welding joint. this work reviews the influence of some operational and engineering parameters that may affect the performance of the friction stir welding and consequentially the mechanical properties of the welding joint..