The effect of FSW parameters on the macro/micro-galvanic corrosion of the dissimilar joint between AZ31 and AA5052

Abstract

In this study, dissimilar friction stir welding was performed between AA5052 aluminium and AZ31 magnesium alloys using a variety of parameters. The results revealed that the optimal range of welding parameter is between 20 and 38 rpm/mm.min−1 (the ratio of rotation speed to travel speed). The findings of the X-ray diffraction and Micro-hardness tests on the stir zone indicated that when the rotation speed is increased, it leads to the formation of intermetallic compounds such as Al12Mg17 and Al3Mg2. The polarization test was used to assess the corrosion rate in various zones. The corrosion rate in the stir zone is higher than in other zones due to macro-galvanic couple between Al and Mg. Additionally, the corrosion rate in the stir zone of sample welded at highest rotation speed of 750 rpm is 1.6 mA cm−2, which is nearly 2.24 times higher than the corrosion rate in other samples. That is attributed to the micro-galvanic coupling of intermetallic compounds (cathode) to the matrix (anode), as well as the macro-galvanic coupling of AA5052 aluminium to AZ31 magnesium alloys.