Areas of concern in an anodised dissimilar friction stir weld of AA5083 and AA6082 aluminium alloys

The major areas of concern when anodising a dissimilar friction stir weld of AA5083-O and AA6082-T6 aluminium alloys in sulphuric acid solution have been investigated. As expected, variations in the specific volumes of structurally transformed substrate materials across the weld zones were observed. Nonetheless, the greatest area of concern is the boundary region between the materials from the advancing side and materials from the retreating side. Mg-Si rich particles were observed to be distributed along the boundary between the two alloys and they possibly contribute to the dissolution in the boundary region when the weld is anodised in 4 M sulphuric acid solution. However, this dissolution was not observed when the weld is anodised in 0.4 M H2SO4 solution.