Influence of welding parameters on material flow, mechanical property and intermetallic characterization of friction stir welded AA6063 to HCP copper dissimilar butt joint without offset

Joining of dissimilar aluminium-copper is an emerging area of interest for both research and industry due to its complex nature. Friction stir welding was attempted to evaluate the joint strength without offset at the butt line between AA6063 to HCP copper sheet under different combination of rotational speed of 800 and 1000 r/min and travel speed of 20 and 40 mm/min. Material flow was studied in detail for different combinations of parameters with optical microscopy and elemental mapping by energy dispersive X-ray spectroscopy (EDS). The results were correlated with the microstructural characteristics and formation of intermetallics at the bond interface using microhardness test and X-ray diffraction (XRD) technique. Material flow clearly suggests that energy input at 800 r/min and 20 mm/min is sufficient to plasticize both the materials with formation of higher amount of thermodynamically stable and hard intermetallic phases Al4Cu9 and AlCu4 (slower cooling rate of 88 K/s) than that at 800 r/min and 40 mm/min (faster cooling rate of 154 K/s), attributed maximum joint strength (∼78.6% of aluminium base metal).