Thermographical analysis of friction stir welding and laser assisted friction stir welding

Friction Stir Welding (FSW), developed at The Welding Institute (TWI) in 1991, is a new solid-state welding process. In this technique, the material does not reach the fusion but the joint is the consequence of the plasticization resulting from the generation of heat by friction and the stirring action of the pin on the material due to the rotation and the displacement of a non-consumable tool. Thus, the FSW reaches temperatures lower than those reached by conventional fusion welds. Laser Assisted Friction Stir Welding (LAFSW) is a combined welding technique in which the FSW is assisted, during the weld, by the pre-heating of a de-focalized laser. This technique leads higher welding speeds, lower clamping force and it has some benefits for tool wear. Nevertheless the control of the temperature field is fundamental to guarantee a high quality joint. In this work FSW and LAFSW bead on plate tests were conducted on 6 mm thick 5754H111 aluminium alloy plates with constant tool rotation and welding speed. Thermographic images were acquired to compare the effect on the temperature field of laser source distance from the tool and laser power