Welding Properties of Dissimilar Al-Cu Thin Plate by a Single-Mode Fiber Laser

Abstract

To improve the reliability and safety of the electrical components used in automobiles, Cu and Al have recently been employed as electrodes, wherein lasers were used for rapid welding. However, in Al-Cu dissimilar metal welding, intermetallic compounds (IMCs) reduce the weld strength. In addition, the laser absorption rates of Al and Cu are low, and the reflectance is high, thereby impeding the welding process. To increase the absorption rate, a laser with a high beam quality must be used. Thus, a high-density, high-quality 5 kW single-mode laser was employed. Thin Al and Cu (0.2 mm thick) plates were processed and welded at welding speed 200–1000 mm/s, changing the laser-irradiated upper metal to Cu or Al. Post analysis, it was found that with a high heat input, pores were generated inside the Al, and when the upper metal was Cu, pores were mainly generated between the Al molten layer and the Cu mixed layer. As a result of tensile shear strength measurement, most of the aluminum area fractured at 118–151 N, and when fractured in copper, the strength was highest at 154 N. At a high welding speed, fracture was mainly observed at the joints along the IMCs or in the Cu mixed layer.