Effect of Processing Parameters on Microstructure and Corrosion Behavior of Friction Stir Welded 7075 Aluminum Alloy

Friction stir welding (FSW) for 1.6 mm thickness 7075 aluminum alloy sheets with different processing parameters was carried out. Based on the analysis of the microstructures of the joint surface, the corrosion behavior was investigated by immersion test. The correlation between the micro-hardness distribution and the corrosion was discussed. The results showed that the grains in the shoulder active zone (SAZ) were obviously refined with the increase of the rotational speed. The spans of the thermomechanically-affected zone (TMAZ) widened and the hardness in the SAZ increased with the increase of the rotation speed. The SAZ corroded worse than other regions. Exfoliation corrosion attack occurred predominantly in the SAZ after being immersed for 4 hours in EXCO solution, and the exfoliation corrosion extended from the SAZ to heat-affected zone. The hardness softened zone was the corrosion sensitive region.