TY - EJOU
AU - Dai, Donghua
AU - Gu, Dongdong
AU - Ge, Qing
AU - Ma, Chenglong
AU - Shi, Xinyu
AU - Zhang, Han
TI - Thermodynamics of Molten Pool Predicted by Computational Fluid Dynamics in Selective Laser Melting of Ti6Al4V: Surface Morphology Evolution and Densification Behavior
T2 - Computer Modeling in Engineering \& Sciences
PY - 2020
VL - 124
IS - 3
SN - 1526-1506
AB - The three-dimensional physical model of the randomly packed powder
material irradiated by the laser beam was established, taking into account the
transformation of the material phase, the melt spreading and the interaction of
the free surface of the molten pool and the recoiling pressure caused by the material evaporation during the selective laser melting. Influence of the processing
parameters on the thermal behavior, the material evaporation, the surface morphology and the densification behavior in the connection region of the molten
pool and the substrate was studied. It was shown that the powder material underwent the transformation from the partial melting state to the complete melting
state and finally to the overheating state with the applied laser energy density
increasing from 167 J/mm3 to 417 J/mm3
. Therefore, the solidified track ranged
from the discontinuous tracks with the rough surface to the continuous tracks with
residual porosities, then to the continuous and dense tracks and terminally to the
fluctuated tracks with the increase in the laser energy density. Meanwhile, the
laser energy effect depth was maintained the positive relationship with the laser
energy density. The vortex velocity obtained in the free surface of the molten pool
towards to the rear region in the opposite laser scan direction promoted the melt
convection to the edge region of the molten pool as the laser energy density was
higher than 277 J/mm3
, demonstrating the efficient energy dissipation from the
center of the irradiation region to the whole part of the molten pool and the attendant production of the sufficient melt volume. Therefore, the efficient spreading of
the molten pool and the metallurgical bonding ability of the melt with the substrate was obtained at the optimized laser energy density of 277 J/mm3
. However,
the severe material evaporation would take place as the melt was overheated,
resulting in the formation of the residual pores and poor surface quality.
KW - Additive manufacturing; melt convection; surface morphology; densification behavior; numerical simulation
DO - 10.32604/cmes.2020.010927