Microstructure and interfacial behavior of SiC_p/6061 aluminum matrix composite joined by laser welding with filled Ti_xSi powder

SiC_p/Al matrix composites exhibit excellent thermal and mechanical properties, making them highly desirable in aerospace, automobile, and electronics industries. However, a drawback arises during the welding process, wherein the brittle Al₄C₃ compound tends to form in the weld joint of SiC_p/Al matrix composites, leading to a significantly diminishes the toughness and strength. To mitigate the issue of brittle Al₄C₃ formation in the weld joint, laser welding with Ti_xSi powders as a filler was employed. The microstructure, interfacial behavior and microhardness of the SiC_p/Al matrix composites in the weld joint were characterized. The results reveal that the weld beads are smooth and uniform, with no observed pores, cracks, sparks, or other defects. Within the weld joint, there are TiC particles and bulk Al₃Ti present, and notably, no needlelike Al₄C₃ phase is found in the zone. As the Ti/Si molar ratio of the mixed powder Ti_xSi increases, the number and volume of the bulk phase reach a peak value at the molar ratio of 3:1 (Ti₃Si). The weld interface zone consists of five layers: a serration-shaped layer near the base materials, a layer with white particles, a layer with white slender reticular structures, and chrysanthemum-like structures. Additionally, numerous white particles form around the SiC particles in the interface zone. The microhardness value of the weld joint initially decreases and then increases with the increase in the Ti/Si molar ratio of the Ti_xSi filler powder, and the minimum microhardness value is about 148.6 HV for the Ti₂Si.