2023 Volume 64 Issue 753 Pages 188-193
Tailor welded blanks (TWBs) are considered a suitable method to achieve the light-weighting of automobiles efficiently, and the use of dissimilar metal TWBs may further enhance the effect. To produce steel/aluminum alloy TWBs with high weld strength, friction stir welding is useful, and previous research has revealed that an artificial re-aging treatment after welding further increased the weld strength. However, galvanic corrosion would cause the depression of reliability for such TWBs. In this study, the combined cycle corrosion test was conducted for SPCC/A6061P-T6 joined by friction stir welding. Before the corrosion test, the effect of the artificial re-aging treatment after welding was preliminarily investigated. From experimental results, it was confirmed that these treatments enhanced weld strength by 20-30%. After that, the combined cycle corrosion test was conducted for as-welded and treated SPCC/A6061P-T6 TWBs. As a result, we found that almost no change occurred in weld strength until around the 20th cycle, and after that, the weld strength decreased moderately. Beyond the 30th cycle, weld strength decreased rapidly and practically disappeared around the 40th cycle for as-welded blanks and around the 50th cycle for treated blanks. From the results of observation using FE-SEM and EDS analysis, the mechanism of the decrease in weld strength was clarified.
