Abstract
Powder spattering and splashing in the melt pool are common phenomena during Laser-based Powder Bed Fusion (LPBF) of metallic materials having high fluidity. For this purpose, analytical and computational fluid dynamics (CFD) models have been deduced for the LPBF of AlSi10Mg alloy. The single printed layer’s dimensions were estimated using primary operating conditions for the analytical model. In CFD modelling, the volume of fluid and discrete element modelling techniques were applied to illustrate the splashing and spatter phenomena, providing a novel hydrodynamics CFD model for LPBF of AlSi10Mg alloy. The computational results were compared with the experimental analyses. A trial-and-error method was used to propose an optimized set of parameters for the LPBF of AlSi10Mg alloy. Laser scanning speed, laser spot diameter and laser power were changed. On the other hand, the powder layer thickness and hatch distance were kept constant. Following on, 20 samples were fabricated using the LPBF process. The printed samples’ microstructures were used to select optimized parameters for achieving defect-free parts. It was found that the recoil pressure, vaporization, high-speed vapor cloud, Marangoni flow, hydraulic pressure and buoyancy are all controlled by the laser-material interaction time. As the laser-AlSi10Mg material interaction period progresses, the forces presented above become dominant. Splashing occurs due to a combination of increased recoil pressure, laser-material interaction time, higher material’s fluidity, vaporization, dominancy of Marangoni flow, high-speed vapor cloud, hydraulic pressure, buoyancy, and transformation of keyhole from J-shape to reverse triangle-shape that is a tongue-like protrusion in the keyhole. In the LPBF of AlSi10Mg alloy, only the conduction mode melt flow has been determined. For multi-layers printing of AlSi10Mg alloy, the optimum operating conditions are laser power = 140 W, laser spot diameter = 180 µm, laser scanning speed = 0.6 m/s, powder layer thickness = 50 µm and hatch distance = 112 µm. These conditions have been identified using sample microstructures.
Highlights
Additive manufacturing (AM) provides customized design, reduced processing time and the ability to create complicated shapes
The samples were cut in the dimensions of 2.5 × 10 × 50 at the Additive Manufacturing Technology Application and Research Center (EKTAM), Gazi University, Turkey
For laser powder bed fusion (LPBF) printing, powder layer thickness and hatch distance were set as 50 μm and 112 μm, respectively
Summary
Additive manufacturing (AM) provides customized design, reduced processing time and the ability to create complicated shapes It has garnered a lot of attention from sophisticated technological applications [1], aerospace [2], biomedical [3,4,5] and construction [6,7]. Amongst the most sophisticated and efficient AM processes is laser powder bed fusion (LPBF) [8,9]. In this process, a laser beam is used to fuse the particles [10]. Heating dynamics and cracking processes are strongly influenced by conduction [12], due to the numerous physical processes involved in LPBF, such as laser-matter interactions and melting-solidification hysteresis. One can identify that the LPBF multi-physics is a combined effect of heat transfer and temperature at the interface [13,14,15]
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