Simulation And Experimental Study On Absorption Behavior Of Aluminum Alloy Based On Selective Laser Melting

In this paper,a three-dimensional mesoscopic model was proposed and the ray-tracing method was used to investigate the laser absorption behavior during selective laser melting(SLM)based on aluminum alloy and Al based composite powder particles.The model fully considered Fresnel absorption of S and P polarization,as well as the multiple reflections between the powder particles and the randomly packing powder-bed.The simulation deeply explored the laser absorption mechanism of the loose powder bed model under an established three-dimensional Gaussian light source.In the model of ideal close-packing,the absorptivity of the aluminum alloy powder bed with different particle size distribution(10 ?m,20 ?m,30 ?m,40 ?m,50 ?m and 60 ?m)and the irradiance distribution of the particle surface were discussed.It was found that powder particles with small particle size enhanced the multiple reflection and interactions between the laser and powder particles,causing higher laser absorptivity and the irradiance.These brought enough temperature and accumulated energy,which lead to the full melting of powder.To verify the reliability of the simulation results,the SLM experiments with different particle sizes under the same process parameters were performed.The forming quality of experimental samples were analyzed and the results showed good agreement with simulation.In order to further optimize the actual powder bed model,this study adopted the sequence addition method to obtain the three-dimensional randomly packing powder bed model and the effect of reinforcing particles on the laser absorption behavior was investigated.In the simulation process,by adding small-size Si C and Ti B2 reinforcements particles,a randomly distributed powder bed model of Al based composites was established for ray-tracing calculation.It was found that the reinforcements particles increased the laser-receiving area of the powder bed and significantly increased the absorptivity and irradiance distribution.The increase of the laser ray track spots on the particles surface indicated that the interaction between laser and powder particles were strengthened.The interactions were illustrated by counting laser ray track spots on the particles surface.In addition,due to the superior optical parameters of Si C,the absorption enhancement effect of Si C particles on the laser absorptivity is slightly larger than that of Ti B2 particles.Finally,the experimental verification was designed with the same processing parameters as the simulation.The SLM-processed particle reinforced Al based composite material obtained more absorbed irradiance than pure Al Si10 Mg.The temperature of the liquid phase in the molten pool was increased,which was beneficial to improve the wetting behavior of molten pool,which induced the liquid phase in the melting process can be smoothly spread,the metallurgical bond between adjacent scanning tracks was reasonably strengthened.The SEM analysis of the sample showed that the particle reinforced Al based composite formed a larger volume of the molten pool,the surface quality was more stable,the degree of densification and microhardness was higher,which proved the accuracy of the simulation.