Friction stir spot welding of aluminum and steel sheets using a consumable sheet

A novel method, friction stir spot welding using a consumable sheet (FSSW-C), is introduced here with the aim of joining dissimilar sheets. In this process, faying surfaces of the base materials are kept at a specific gap, and a consumable sheet is placed on the top of the base materials. When the tool progresses into the consumable sheet, the plasticized consumable material gets extruded into the gap and joining occurs between the base materials. The tool never touches the steel base material overcoming the tool wear problem. In the present work, AA6063-T6 and CRCA/IS-513 are the base sheets, and AA6063-T6 is the consumable sheet. The effect of tool rotational speed on the joint formation, interface characteristics, microhardness, temperature evolution, lap shear strength, bend shear strength, and fracture modes have been analyzed. Microstructural zones are also revealed. The rotational speed of 900 rpm is the best choice for FSSW-C of AA6063-T6 and CRCA/IS-513 sheets, keeping 2-mm/min plunge speed, 2-mm plunge depth, 5-s dwell time, and 1.5-mm gap constant. However, additional case studies reveal a plunge depth of 1.5 mm (at 900 rpm) as a better choice due to further lap shear fracture load improvement.