Influence of metal surface groove depth on FSLW of 6061-T6 Al alloy and CFRTP

Lightweighting plays a crucial role in product engineering applications. Polymers exhibit broad applications and development prospects due to their excellent mechanical properties. Friction stir welding (FSW) is a robust joining technology for metal/polymer combinations. In this study, various depths of surface grooves were created on the aluminum (Al) alloy sheets. Carbon-fiber-reinforced thermoplastic composites (CFRTP) and Al alloy sheets were welded using friction stir lap welding (FSLW). An infrared temperature camera captured the welding temperature. The microstructure of the joints was analyzed using an optical microscope (OM), and the tensile properties were evaluated through tensile tests. The results indicated that the surface groove facilitates the mixture of different materials, the formation of mechanical interlock, and the adhesion between different materials, thereby enhancing the reliability and tensile strength of the dissimilar material joint. The maximum tensile strength is 38.01 MPa, representing 71.71% of the CFRTP base strength. However, excessive depth leads to the formation of tunnels on the welding seam surface, resulting in significant defects in the joint. Surface temperature has a negative correlation with groove depth; however, it has a minimal effect on dissimilar material mixing in the joint.