Study on the Microstructure and Mechanical Properties on Al/Carbon Fiber Reinforced Thermoplastic Dissimilar Friction Stir Lap Welding Joints

Friction stir welding (FSW) of dissimilar metals and polymers has shown some attractive applications in industrial fields such as drone tails and automotive parts. Adjusting process parameters is a fast and effective method to improve the tensile performance of joints. In this paper, the evaluation of friction stir lap welded joints between 6061-T6 aluminum alloy and carbon fiber reinforced thermoplastic (CFRTP) is conducted by studying the microstructure characteristics of the weld interface, SEM of the fracture surface, tensile and hardness analysis. The results indicate that the upper part of the weld cross-section joint experiences longer stirring and friction durations. The small metal fragments broken at the lower part of the joint are recombined into larger fragments. At high rotational speeds, the formation of welds is faster and more uniform. Metal fragments are further broken and refined and the molten CFRTP is uniformly mixed with Al alloy fragments in the stirring zone, which improvs the bonding property between two materials. Therefore, the value of tensile strength at 1800 rpm reaches 32.9 MPa, which is equivalent to 63.1% of CFRTP sheets.