Investigation on mechanical properties and corrosion behavior of dissimilar joints of 5083 and 6005A alloy welded by friction stir welding

Abstract

AbstractIn this paper, the microstructure, mechanical properties, and corrosion behavior of friction stir welded (FSW) joints of the two aluminum alloys 6005A‐5083 were investigated and their correlation was discussed. In contrast to FSW joints of the same aluminum material, this results in a “V” shape curve of hardness distributed nonsymmetrically along the weld. The lowest hardness area occurs at the interface between the heat‐affected zone and the thermo‐mechanically affected zone of 6005A (6‐HAZ and 6‐TMAZ) due to the transformation of the β" phase under the influence of heat input during the stir friction process. This also leads to all tensile specimens fracturing in this area. The corrosion behavior of the FSW joint in acidic solution containing Cl− was determined by an exfoliation corrosion (EXCO) test, an intergranular corrosion (IGC) test, and potentiodynamic polarization measurements, based on the potential application in acid rain environment. The results showed that the corrosion resistance order in the acidic solution is: 6‐HAZ > NZ > 6‐BM > 5‐HAZ > 5‐BM. The 5‐BM has the worst corrosion resistance due to the high corrosion sensitivity of Al3Mg2 in acidic solution. However, good corrosion resistances are shown in NZ and 6‐HAZ, which is related to a relatively homogeneous microstructure in NZ and a dissolution or coarsening of β" phases in 6‐HAZ because of frictional heat input.