Al₄C₃-free joining of SiC_p/Al composites achieved via ultrafast laser welding

Ceramic-reinforced aluminum matrix composites possess exceptional properties, which makes them promising candidates for a wide range of applications. However, the brittle Al₄C₃ phases, which can severely deteriorate the properties of the joint, are often formed in the joint obtained using conventional fusion welding techniques. In this study, an ultrafast laser welding approach is adopted for the first time to join aluminum matrix composites reinforced with 45 vol.% SiC particles. The achieved joints appear to be sound, free from macroscopic defects, and the four-point bending strength of the joint can reach 321 MPa. The effects of laser power and welding speed on the microstructure and mechanical properties are systematically examined. Comprehensive characterization reveals that, unlike conventional laser welding, no brittle and hydrolyzable Al₄C₃ phase is detected in the welding seam. Instead, the ultrafast laser irradiation promotes the decomposition of SiC particles, which subsequently react with molten aluminum to form nanoscale Al₄SiC₄ phases. These precipitates are uniformly dispersed throughout the matrix, thus enhancing the joint performance.