Dissimilar lap welded joints of copper and brass metals were fabricated by friction stir welding (FSW) method at various welding heat inputs. The effect of welding heat inputs on the microstructure and mechanical properties of overlap welded joints at at two different join configurations (i.e. Advancing side and Retreating side joint configurations) was investigated. In both joint configurations, copper and brass plates are located on the top and bottom plates, respectively. Tensile-shear and vicker's microhardness tests were conducted to evaluate the mechanical properties of dissimilar lap welded joint. In order to analysis of microstructure and fracture surface of lap welded joints, optical microscope (OM) and scanning electron microscope (SEM) were used. The ontained results showed that the weld surface of samples was appeared without groove defects, low superfluous flash and oxidation, when the welding heat input is increased. Onion ring pattern characterized by the stack of copper and brass metals is identified in the weld nugget zone (WNZ) where metal flow structures can be observed. With decreasing welding heat input, tensile-shear strength increased at both joint configurations. The highest hardness was exhibited in the WNZ with increasing welding heat input in both joint configurations.

The corrosion behavior at different positions (top and bottom) of the weld nugget zone along the thickness plates in AA6061-T6 aluminum alloys welded by friction stir lap welding, under the conditions of 1000 rpm-60 mm/min and 900 rpm-40 mm/min in a 3.5 wt% NaCl solution, was investigated by Tafel polarization at ambient temperature. The morphology of the nugget zone corroded surfaces was analyzed by scanning electron microscopy together with energy dispersive spectroscopy (SEM-EDS) as well as atomic force microscopy (AFM). It was found that the top half of the nugget zone has a better corrosion resistance than that of the bottom half for both welding conditions. A localized pit dissolution with combined intergranular corrosion are the dominant corrosion types across different positions of the nugget zone for various welding conditions and in the parent alloy.

In this work, the corrosion behaviors of friction-stir lap welding of 6061-T6 Al-alloy are studied. The friction-stir lap welding was performed under different welding conditions (rotation speed and welding speed). The corrosion behavior of the parent alloy, the weld nugget zone (WNZ), and the heat affected zone (HAZ) of each welded sample working as an electrode, were investigated by the Tafel polarization test in 3.5 wt. (%) NaCl at ambient temperature. The morphology of the corroded surface of each region was analyzed by scanning electron microscopy together with energy dispersive spectroscopy (SEM-EDS). The results showed that the corrosion resistance of the parent alloy was better than the WNZ and the HAZ in both welding conditions. Localized pit dissolution and intergranular corrosion were the dominant corrosion types observed in the parent alloy, WNZ, and HAZ. The parent alloy, WNZ, and HAZ exhibited similar corrosion potentials (Ecorr) after T6 heat treatment. This treatment had a better effect on the corrosion resistance of the welded regions than the parent alloy.