A holistic simulation chain for the laser powder bed fusion process for metals at particle scale

  • Mohseni-Mofidi, Shoya (Fraunhofer IWM)
  • Dietemann, Bastien (Fraunhofer IWM)
  • Najuch, Tim (Fraunhofer IWM)
  • Butz, Alexander (Fraunhofer IWM)
  • Bierwisch, Claas (Fraunhofer IWM)

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It is very challenging to develop a holistic numerical simulation of the laser powder bed fusion process for metals (PBF-LB/M) at particle scale since a great variety of physical phenomena take place simultaneously. To tackle this, we take advantage of different numerical models each of which is appropriate to represent an aspect of the process ranging from the deposition of powder to the final material properties. The Discrete Element Method (DEM) is employed to model the powder spreading process yielding realistic powder layers. Ray Tracing (RT) is employed to calculate the laser energy deposition in the material as multiple reflections are considered. The thermo-viscous and thermo-capillary flow of the melt pool are then studied by using Smoothed Particle Hydrodynamics (SPH) simulations. The thermodynamic approach of CALPHAD is utilized to obtain material properties required for the SPH simulations. A Cellular Automaton (CA) is used to calculate the growth of dendritic grains based on the temperature field in the melt pool, and consequently to predict the size and shape of microstructure grains formed during solidification. This microstructure serves then as an input for Crystal Plasticity Finite Element Method (CP-FEM) simulations to qualitatively describe texture dependent mechanical properties such as the elastic modulus or the yield stress. A series of validation cases will be presented. A posteriori measured melt pool dimensions are assessed for Inconel 718 while in situ melt pool dynamics are studied for TI6Al4V [1]. The transition from conduction mode to keyhole mode as a function of scan speed and energy input is compared for several alloys [2]. Residual porosity and lack of fusion are analyzed for a novel Al-Ni alloy. The microstructure grain morphology is compared for AlSi10Mg. Quantitative agreement or distinct qualitative correspondence between simulations and experiments is found in all these cases. In summary, using the presented simulation chain, the PBF-LB/M process can be investigated with a high degree of detail. This does not completely replace corresponding experiments but provides a tool to gain a better understanding of process-structure-property relationships. Thereby, the manufacturing of existing material systems can be improved and the development of new alloys for the PBF-LB/M process is supported.