Effect of active forced cooling on microstructure and corrosion properties of friction stir welded Al/Cu dissimilar joints: Quasi-in-situ study

Corrosion resistance is a critical service performance of the Al/Cu dissimilar joints. Using the effect of forced cooling of flow water, a submerged friction stir welding (SFSW) technology was developed to enhance the corrosion resistance of the Al/Cu joints. The weld formation of the joints was not only improved by active forced cooling, but also it could refine the grains of the WNZ, and effectively reduce the interfacial IMCs layer thickness. The potential difference between the Al and Cu gives rise to the formation of a macroscopic galvanic effect, which accelerates the corrosion of the joints. Nevertheless, the corrosion resistance of SFSW joints was higher than that of FSW joints. During the 240 h corrosion period, no significant corrosion occurred on the Cu side due to cathodic protection, while the heat affected zone (HAZ) of Al side suffered the most severe corrosion, forming distinct corrosion grooves. Compared with the FSW joint, the SFSW joint had smaller width and depth of corrosion grooves on the HAZ of Al side, with a significantly reduced overall corrosion degree. It demonstrates that the active forced cooling contributes to improve the microstructure and corrosion resistance of Al/Cu joints.