Ablated surface morphology evolution of SiCp/Al composites irradiated by a nanosecond laser

Metal matrix composites are widely used in aircraft and aerospace components due to their low weight and high strength. Since their processing by conventional methods is quite problematic, laser processing techniques have to be used and optimized. In this study, two SiC particle-reinforced Al matrix composites with different volume refractions and average particle sizes, namely SiCp/AA2024 (45%, 30 μm) and SiCp/AA6061 (60%, 3 μm) were irradiated by a nanosecond laser with a pulse fluence range of 0.68–6.83 J/cm2. The ablated surface morphology evolution was studied by SEM, and the elements' distribution was analyzed by EDS. At increased pulse fluence, the molten matrix firstly spilled from spaces between silicon carbide particles and then spread on their surfaces, forming a smooth surface in the first composite with small particle size but failing to cover SiC particles in the second one with large particle size. The SiC particles on the laser-treated surface were seriously oxidized, while distributions of Al and Si elements on the laser-ablated surfaces were independent. The dispersion of Si element increased with the fluence. The ablation threshold and surface roughness of SiCp/AA6061 was lower than those of SiCp/AA2024, in contrast to the ablation depth. The performed thermal simulation confirmed the heat conduction existence between the matrix and reinforcement, as well as the particle's volume refraction and average size effects on the heating behavior of SiCp/Al composites. The results obtained are considered instrumental in substantiating the applicability of various laser processing techniques to SiC particle-reinforced Al matrix composites.