Selective Laser Melting Of TiC Nanoparticle Reinforced Al-based Composites: Simulation And Experiments

In order to comprehensively understand the process of selective laser melting(SLM) of TiC nanoparticle reinforced Al-based composites, a transient three-dimensional model was established, using a finite volume method(FVM). Some important physical phenomena, such as transition from powder to solid, nonlinearities produced by temperature-dependent material properties and the Gaussian distributed laser heat source, were taken into account in the calculation. The effects of laser power and scan speed on temperature evolution behavior, molten pool dimensions and liquid lifetime were thoroughly investigated. The simulation results showed that Marangoni convection played a crucial role in intensifying the convective heat transfer and changing the molten pool geometry. The temperature of laser-powder interaction zone, the molten pool dimensions and liquid lifetime increased with increasing laser power or decreasing scan speed. The maximum temperature gradient within the molten pool increased significantly with increasing the applied laser power, but increased slightly as a higher scan speed was applied. The experimental study on the inter-layer bonding and densification behavior and the surface morphologies and balling effect of the SLM-processed TiC/AlSi10 Mg nanocomposites parts was performed. The experimental results validated that the dense and coherent metallurgically bonded layers without any apparent cracks and pores were generated as the laser processing parameters were optimized at P = 150 W and V = 400 mm/s. Meanwhile, a pretty dense and smooth surface was yielded, free of any balling effect and pores formation when P = 100 W and V = 150 mm/s were applied.The influence of laser energy per unit length(LEPUL) on heat and mass transfer, melt pool dynamics, and particles rearrangement was investigated. It showed that the Marangoni convection became more vigorous with an increase of LEPUL, accordingly enhancing the thermal capillary force. The high laser energy input induced a sufficient liquid formation and an improved wettability, lowering the friction force exerting on TiC solids. Under this condition, the reinforcing particles can be well mixed within the matrix. The experimental study on the distribution state of TiC reinforcement in the SLM-processed Al matrix was performed. The results validated that the dispersion of TiC reinforcement changed from a severe aggregation to a uniform dispersion in the matrix with the increase of LEPUL. Meanwhile, the mean particle size of the TiC reinforcement also increased with the increase of LEPUL. As LEPUL increased to1000 J/m, the average particle size of TiC increased to 134 nm, losing its original nanoscale structure.Numerical simulation adopting the Gaussian distributed volumetric heat source was performed to investigate the influence of reinforcement weight fraction on thermal evolution behavior and fluid dynamics during selective laser melting(SLM) additive manufacturing of TiC/AlSi10 Mg nanocomposites. The simulation results showed that the increase of operating temperature and resultant formation of larger melt pool were caused by the increase of weight fraction of reinforcement. The circular flows appeared when the TiC content reached 5.0 wt.% and the larger-sized circular flows were present as the reinforcement content increased. The experimental study on microstructures on the polished sections of SLM-processed TiC/AlSi10 Mg nanocomposite parts was performed. With the increase of TiC content, the distribution state of TiC reinforcement changed from disordered structure to the novel ring structure, which was consistent with the simulation results.