A New Investigation into Al-Cu Dissimilar Joint by SiC Nanoparticle during the FSSW Process: Influence of Rotational Speed and Dwell Time

Abstract Friction stir spot welding (FSSW) was implemented to joining of AA2024-T4 and commercially pure copper with SiC nanoparticles as a reinforcing particle for the first time. The influence of welding parameters namely rotational speed (1300, 1600, and 1900 rpm) and dwell time (2, 4, and 6 s) on microstructure and mechanical characteristics of the welds were studied. For this purpose, macro-and microstructures, shear tensile strength, and microhardness of the joints were investigated. The grain size of the stir zone on copper and aluminum sides decreases from 45.1 to 10.5 µm and 62.2 to 14.5 µm as rotational speed and dwell time decrease. Furthermore, the size of the weld zone increased as rotational speed and dwell time increased. The results revealed the formation of AlCu and Al2Cu intermetallic compounds in the weld zone. The thickness of the IMCs layer in the interface joint increases as input heat increases. It was found that there is a direct relationship between the shear strength of weld specimens and rotational speed and dwell time during the FSSW process. The microhardness value of the joint zone was significantly improved from HV 122 to HV 156 with an increase in rotational speed and dwell time.