Characteristics of Mechanical Properties and Microstructure of Micro Friction Stir Spot Welding of AA1100 and Brass

Friction stir spot welding (FSSW) is a type of solid state welding that has been widely developed using both similar and dissimilar materials. Aluminum AA1100 (99% Al) and brass (Cu-Zn) with a thickness of 0.42 mm are used in this welding joint. This research investigates the characteristics of the lap shear force and microstructure of micro FSSW joints on similar aluminum alloy AA1100, similar brass, and dissimilar AA1100–brass materials using a pin tool made of high-speed steel. The constant process parameters of the micro FSSW joint were plunge depth, dwell time, plunge rate, and high tool rotational speed of 0.7 mm, 6 s, 4 mm/min, and 33,000 rpm, respectively. Micro FSSW joints were carried out on similar AA1100, similar brass, and dissimilar materials whereby AA1100 was the upper sheet and brass was the lower sheet. The results of this research show that micro FSSW joints have a higher lap shear force on similar materials than dissimilar materials. The number of spots on the similar AA100 had no significant effect on the lap shear force, while with similar brass, the number of spots had a significant effect on lap shear force. The formation of a very thin intermetallic compound layer in the nugget zone occurred in the dissimilar materials. Moreover, observation results indicate that the similar AA1100 and similar brass had a lap shear force with a plug fracture type, while the type of fracture found in dissimilar materials was the interface failure mode.