Numerical Investigation On Temperature Field And Stress Field During Selective Laser Melting Of AlS10Mg

Finite element simulation of temperature field during selective laser melting(SLM) of Al Si10 Mg powder was performed using the ANSYS software. The effects of laser powder and scan speed on the SLM thermal behaviors were investigated. It showed that the cooling rate and temperature gradient of the molten pool elevated as the laser power increased. Moreover, the laser power had the more remarkable effect on the temperature gradient. As the scan speed increased, the cooling rate of the molten pool enhanced significantly, but the temperature gradient of the molten pool decreased slightly. The liquid lifetime and dimensions of the molten pool also increased gradually with the increase of laser power or the decrease of scan speed. A sound metallurgical bonding between the neighboring fully dense layers was achieved at laser power of 250 W and scan speed of 200 mm/s, due to the larger molten pool depth(67.5 μm) as relative to the layer thickness(50 μm).Based on the simulation results of temperature field, a finite element model was developed for studying stress field during SLM of Al Si10 Mg powder using an indirect thermal-mechanical coupling method. The influences of laser powder and scan speed on the evolution of SLM thermal stress and the distribution of residual stress were also investigated. It showed that the SLM thermal stress fluctuated with the moving laser spot. Expansion deformation occurred in the laser irradiation zone, and the zone near melt pool was in compressive stress state with the negative σx and σy. The laser scanned zone was mainly in tensile stress state. Moreover, the stress along the scan direction(σx) was greater than the stress vertical to the scan direction(σy). The residual tensile stress was distributed on the top surface of SLM-fabricated component, the middle zone of which had the higher stress than the edge. The maximum residual stress was located at the interface of the melted layer and the substrate where warping or cracking tended to occur. The maximum residual stress elevated from 257 MPa to 340 MPa as the laser power increased from 200 W to 300 W, and it enhanced from 257 MPa to 270 MPa as the scan speed increased from 200 mm/s to 400 mm/s. The residual stress was more sensitive to the laser power than the scan speed.SLM of Al Si10 Mg powder was also experimentally performed using different laser processing conditions and the microstructures of the SLM-fabricated samples were investigated to verify the reliability of the physical model. The SLM-fabricated component with the smooth surface and free of pores or cracks was achieved at laser power of 250 W and scan speed of 200 mm/s. Finally, residual stresses on the top surface of SLM-fabricated component were measured using the micro-indentation method. Comparison of the measurement data and the simulation results, it showed that the simulation results were in accordance with the measurement. The numerical simulation can successfully predicate the influences of laser processing parameters on the residual stress of SLM-fabricated component.