Microstructure and corrosion characterization of the nugget region in dissimilar friction-stir-welded AA5083 and AA1050

Metallurgical structure, mechanical properties and electrochemical behavior of dissimilar friction stir welding (FSW) between structural AA5083 and AA1050 alloys were investigated in this study. Optical microscopy and field emission scanning electron microscopy observations showed that the nugget zone (NZ) possesses equiaxed recrystallized grains of the two alloys with a flowing shape. Energy-dispersive spectroscopy analysis revealed that NZ is mainly composed of the advancing side alloy. The ultimate tensile and yield strengths of the dissimilar FSW joint were higher than those of AA1050 and lower than those of AA5083. Consequently, fracture occurred on AA1050 side during the tensile tests. The potentiodynamic polarization (PDP) results revealed that the passive current density of the FSW joint was in between that of AA1050 and AA5083. A modified Randles equivalent circuit was used to simulate the obtained experimental data of electrochemical impedance spectroscopy measurements. The acquired impedance parameters were in good agreement with the PDP measurements.