Laser absorption behavior of randomly packed powder-bed during selective laser melting of SiC and TiB2 reinforced Al matrix composites

In this paper, a randomly packed powder-bed model by sequential addition method was established mathematically and physically to simulate the condition of the interaction between the laser beam and powder particles. The ray-tracing calculation was used to analyze laser absorptivity and irradiance distribution occurring on powder particle surface as well as the influence of reinforcements on the laser energy absorption during selective laser melting additive manufacturing of pure AlSi10Mg, SiC/AlSi10Mg and TiB2/AlSi10Mg materials. The simulation results reveal that addition of reinforcements enhanced the interactions of laser beam with powder particles, which were illustrated by an increase of laser ray track spots on the particles surface. A respective absorptivity fluctuated from 0.37 to 0.59 and from 0.34 to 0.49 for the randomly packed SiC/AlSi10Mg and TiB2/AlSi10Mg, both of which were significantly enhanced with respective to that of AlSi10Mg powder. The addition of ceramic reinforcement particles can significantly improve the absorption irradiance of laser for powder-bed of pure AlSi10Mg, while the SiC reinforcement was more effective in enhancing this effect than TiB2. The influence of different absorption irradiance on the melt pool dimensions and surface morphologies were studied experimentally to verify the reliability of this simulation.