마찰교반용접(FSW)을 이용한 Cu/Al 이종합금 용접의 특성

Characteristics of Dissimilar Copper-Aluminum Welding Using Friction Stir Welding

In this research paper, we evaluated the weldability of dissimilar materials, copper and aluminum, using friction stir welding (FSW), The specimens used to perform FSW were a copper plate material (2 mm thick) and an aluminum plate material (2 mm thick). The two joining configurations, butt joint and lap joint, were welded using FSW. In order to investigate the weldability of the joints, hardness and tensile tests were carried out on the base material, heat affected zone (HAZ), thermo-mechanically affected zone (TMAZ), and stir zone (SZ). Optical microscopy was also performed to investigate the microstructure of joints. As a result of these tests, the yield strength and tensile strength of the lap joint were measured to be lower than the butt joint. Additionally, these tests caused the center part to elongate in fibrous shape and the heat-affected part was easily broken, resulting in the appearance of a dimple type fracture surface and a microstructure. In the lap joint, specimens showed the cleaved fracture surface with Chevron V-type mark that appeared in the brittle fracture at the shear stage. The analysis of the friction stir welds showed a finer structure than the base metals. Furthermore, the results revealed that the butt joint welds tend to appear clearly than the lap joint welds due to the rotational speed of the tool during the friction welding. Specifically, butt joints exhibited better mechanical and structural properties than lap joints.