Effect of exfoliation corrosion on the efficient hybrid joint of AA2024-T3 and AA2198-T8 formed by friction stir welding

The third-generation alloy, AA2198-T8, is highly recommended for the aerospace industry. However, it has come under scrutiny due to its high cost. This study aims to decrease the cost of manufacturing through a hybrid design that uses AA2198-T8 alloys for the crucial parts and AA2024-T3 alloys for the remaining structure. The two main techniques for joining AA2024-T3 to AA2198-T8 are reversed double-sided friction stir welding (DS-FSW) and traditional single-sided friction welding (SS-FSW). They were carried out under unaltered tool rotation speed followed by five different welding speeds. The mechanical properties of the joints were explored, and the maximum joining efficiency of the welding process was 96% for reversed DS-FSW at 102 mm/min welding speed. The hybrid joint was tested for compliance with ASTM G34 standards to examine the welding joint's exfoliation corrosion (EXCO) for eight exposure times. The findings showed that joint efficiency decreased relative to as-welded joints, and mechanical property deterioration increased with EXCO exposure duration, reaching 40% for specimens exposed for 120 h to the corroding solution. It has been noted that morphology and grain size changes significantly impact EXCO.