Study on Low Axial Load Friction Stir Lap Joining of 6061-T6 and Zinc-Coated Steel

Friction stir lap joining of 6061-T6 and zinc-coated steel was performed using a high rotation speed and small tools with different pin lengths. During the welding process, the average axial force ranged from 0.2 to 1.1 kN, which is smaller than that for conventional friction stir welding. Satisfactory surface formation was achieved using a pinless tool and smaller plunge depth. The highest failure load of 2.26 kN was achieved for a pin length of 0.3 mm, plunge depth of 0.3 mm, and welding speed of 50 mm/min. The specimen fractured at the advance side of the 6061-T6 base metal. A continuous and compact interface layer with a thickness of 5.2 μm was formed. The main component of the intermetallic compound at the interface was Fe₄Al₁₃. The intermetallic compound was tightly connected and bound to the steel galvanized sheet and aluminum side.