In the field of electronic packaging, the preparation and application of traditional electronic packaging materials such as W/Cu and Mo/Cu are relatively mature. However, these materials have high density and low thermal conductivity, which cannot meet the packaging requirements of high-power portable electronic devices. Aluminum matrix composites have higher strength, wear resistance, and economy, which not only can overcome the shortcomings of traditional packaging materials but can also meet the application requirements of electronic packaging. In SiCp/Al composites, SiC particles react with the Al matrix to form needle-like brittle phase Al₄C₃ during high-temperature melting, which diminishes the welding performance of the joint and severely restricts the welding application of the material. Swing laser welding is expected to improve the microstructures and performances of SiCp/Al welded joints by improving the weld-forming morphology and inhibiting pore formation. Few studies have been conducted on the effects of the beam swing on the laser welding of SiCp/Al composites. Accordingly, in this study, the effects of beam swing mode, amplitude, and frequency on the laser welding of SiCp/Al composites were systematically analyzed. The effects of different laser swing modes and process parameters on the laser welding of SiCp/Al composites are revealed by controlling the variable method. The study on the welding microstructure and mechanical properties provides valuable experimental data for obtaining effective welding of SiCp/Al composites.

The test materials were a welding wire with a diameter of 1.2 mm and a SiCp/6005A composite material with dimensions of 60 mm×50 mm×4 mm. The effects of the different swing parameters on the welding properties of the SiC/Al composites were studied using the control-variable method (Table 2). Four modes of laser beam swing were used during welding: Linear, Circular, “8,” and Infinite (Fig. 2). The swing laser welding process parameters were as follows: laser power of 7500 W, defocusing amount of 0 mm; wire feeding speed of 5 m/min, welding speed of 4.2 m/min, and gas flow rate of 15 L/min. Following welding, the weld morphology and microstructure were observed using optical microscope (OM) and scanning electron microscope (SEM). A tensile test was conducted using a universal testing machine. Micro-Vickers hardness was used for the hardness test. We analyzed the effects of the laser oscillation parameters on the weld in terms of the weld morphology, phase structure distribution, yield strength, and hardness distribution of the sample.

Results show that the linear weld formation has a shorter swing path, smaller spot area, more concentrated laser energy density, more continuous weld formation, and more rounded and uniform front and back weld formation. When no swing is applied (swing amplitude of 0 mm), the upper surface of the weld is not flat, and undercutting occurs. When the swing amplitude is increased, the molten pool is heated more evenly, enabling more stable solidification, which in turn reduces the surface roughness (Figs. 3?5). Under different swing modes, the action time of the laser on the molten pool is different, which increases the time required for the SiC reaction to form Al₄C₃. The higher the frequency of the laser oscillation, the shorter is the action time of the laser in the width direction of the weld, and the shorter is the time of the SiC reaction to form Al₄C₃. Therefore, when the swing frequency is 50 Hz, the SiC content is the highest. The effects of different swing amplitudes on the SiC content in the weld are comprehensive. When the swing amplitude is large, the heating area is large, and more Al₄C₃ is formed by the SiC reaction, the lower is the energy density, the more Al₄C₃ is formed by the SiC reaction, and the small swing amplitude group is the opposite (Fig. 7). In general, swing welding is beneficial for refining weld grains. However, an excessively complex swing mode increases the time required for the SiC reaction to form Al₄C₃, thereby reducing the mechanical properties of the welded joint. The fine-grain strengthening effect fails to compensate the strength-weakening effect caused by the Al₄C₃ phase (Fig. 8). When the tensile specimen breaks, the specimen fractures along the weld center enriched by the needle-like brittle phase Al₄C₃. During the tensile process, the pores in the weld are enlarged, and the cracks also extend along the Al₄C₃-enriched area. Al₄C₃ exhibits a weak bond with the aluminum matrix. During the tensile process, the aluminum matrix with better toughness is first stretched, and the shedding of the needle-like brittle phase Al₄C₃ causes the original position of Al₄C₃ to become the beginning position of the crack. Therefore, it cracks along the weld center enriched by the needle-like brittle phase Al₄C₃ (Fig. 10).

Appropriate swing parameters can inhibit the formation of Al₄C₃ from SiC, effectively inhibit pores, obtain a good weld surface and uniform weld structure, achieve a certain tensile strength, and provide good mechanical properties. However, an excessive swing increases the time and range of heat input, promotes the formation of Al₄C₃ from SiC, and weakens its mechanical properties. Thus, good swing parameters are obtained, namely, a 50 Hz swing frequency and 1 mm swing amplitude in linear swing mode.