Projects
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Single track optimization in laser-based directed energy deposition of Ti-6Al-4V
Single-track experiments are routinely used in the optimization of process parameters in additive manufacturing processes. Most of the process parameter optimization studies use a laser spot size of 1 mm or more. Since laser spot size affects the input energy density and in turn the efficiency of the deposition process, it is important to develop process maps every time a laser of different spot sizes is used. In this work, we determine the process maps for a laser of 0.6 mm spot size. By combining the process maps and the metallographic inspection, we estimate the optimum process parameters (laser power, scan speed, powder feed rate) for building Ti6Al4V components using powder-based laser-directed energy deposition(LDED). Single-tracks corresponding to 64 different parameter combinations are deposited. After eliminating the process parameter combinations resulting in defective tracks, the optimum process parameters of 300 W laser power and 720 mm min−1 scan speed is established by considering the relationship between the process parameters and the geometrical features of the deposit. The experimental results are then used to calibrate the modeling parameters of a three-dimensional finite element model for simulating the deposition process.
Outcome:
Process parameter optimization for laser directed energy deposition (LDED) of Ti6Al4V using single-track experiments with small laser spot size, Optics Laser Technology 175 (2024) 110861.
https://doi.org/10.1016/j.optlastec.2024.110861
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Effect of geometry in laser powder bed fusion built Ti6Al4V components
A significant problem associated with LPBF components is the development of high internal residual stress. Considering the challenges associated with stress measurement for additively manufactured complex geometries, sequential thermo-mechanical FE analysis was chosen as an alternative to investigate the residual stress evolution in different geometries. Part-scale simulations with a layer bundling approach have been performed. The component geometry significantly influenced the distribution of residual stresses. Thin wall geometries exhibited symmetrical residual stress distribution with tensile stresses on the surface and compressive in the interiors. As the build height of the thin wall increases, the tensile residual stresses on the surface decrease. Furthermore, the transition from tensile to compressive residual stresses is closer to the surface with increasing build height. In the cylinders and domes, the nature of the residual stresses varies depending on the interior or exterior nature of the surfaces. Increased heat accumulation or reduced heat dissipation in the interior surface of hollow cylinders and domes exhibit compressive residual stresses, while the exterior walls exhibit the typical tensile stresses.
Outcome:
Geometry dependant residual stress development in LPBF-built Ti6Al4V components: Using synchrotron diffraction and finite element methodize (Writing stage)
