Temperature field analysis and process parameter optimization during L-PBF of Al-Mg-Sc-Zr alloy

To improve the relative density and decrease the manufacturing deficiency, a 3D finite element model of multi-layer and multi-track, considering material state transition and temperature-dependent and anisotropic thermal properties, was established and validated to study the temperature field and optimize the process parameters of laser powder bed fusion. The effects of process parameters on cooling rate and liquid lifetime of molten pool were investigated with numerical simulation. Then a process parameter optimization method considering thermal behavior of molten pool, track space overlap of molten pool and VED constraint conditions was proposed to obtain the optimal process parameter window. The results show that the evolution of temperature field tends to be stable till the third layer of powder bed. The cooling rate and liquid lifetime of molten pool are mainly affected by laser power and scanning speed. The influence of process parameters on the overlap rate of molten pool is ranked as follows: laser power > scanning speed > hatch spacing. The laser power of 200-250 W, scanning speed of 0.8-1.0 m/s, hatch spacing of 120-140 mu m, and volumetric energy density of 60-80 J/mm(3) can contribute to a sound metallurgical bonding between the neighbor layers and tracks.