Effect of microstructure evolution on corrosion behavior of 2195 Al-Li alloy friction stir welding joint

In this study, the microstructure and corrosion behavior of 2195-T8 aluminum-lithium alloy friction stir welding (FSW) joint were investigated by the microscopy and salt spray corrosion tests. Results indicated that the base metal was mainly composed of Al2CuLi and Al2Cu phases. New phases of Al3Li, Al3Zr, Al2CuMg and residual Al2CuLi and Al2Cu phases were found in HAZ, and WNZ exhibited Al3Li and Al3Zr phases. The salt spray corrosion tests showed that BM exhibited the highest corrosion susceptibility, which could be attributed to the macro-galvanic effect between different regions. The corrosion rate of the FSW joints was calculated by conducting salt spray corrosion tests in 3.5% NaCl solution at different pH values and spraying time. The corrosion rate decreased with increasing pH values and the average corrosion depth is positively correlated with the corrosion rate. It was also found that the corrosion rate decreased with increasing spraying time, but the average corrosion depth tended to increase with increasing spraying time. In addition, an empirical relationship was established to predict the corrosion rate of 2195-T8 Al-Li alloy FSW joints, which can be used to predict the corrosion rate of the FSW joints.