Experimental Study on Friction Stir Welding of Dissimilar Al 6061 to Trip 780/800 Steel

Friction stir welding (FSW) of dissimilar Al 6061 and TRIP 780/800 steel has been performed under different process parameters, including tool rotational speed, welding speed as well as the relative position of the tool axis to the abutting edge. Temperature and mechanical welding force was recorded during the process. Welding speed has an insignificant effect on either the maximum temperature or welding force. However, it can directly change the length of high temperature duration, which will accordingly influence temperature distribution in the weld and the microstructure. Higher rotational speed can effectively elevate weld temperature through greater amount of heat input. Metallurgical observations on weld cross sections perpendicular to the joint line was performed using both optical and scanning electron microscope. Microstructure evolution was analyzed and related to the force and temperature measurement results during the FSW process.