SIM-AM 2023

Simulation-Based Process Optimization Towards Homogeneous Ti6Al4V L-PBF Components

  • Koenis, Tim (Royal Netherlands Aerospace Centre (NLR))
  • Montero-Sistiaga, Maria (Royal Netherlands Aerospace Centre (NLR))
  • De Smit, Marc (Royal Netherlands Aerospace Centre (NLR))
  • Amsterdam, Emiel (Royal Netherlands Aerospace Centre (NLR))

Please login to view abstract download link

3D printing (or additive manufacturing) is a manufacturing process which is gaining popularity within the aerospace sector thanks to the possibilities offered by this technology to manufacture highly optimized, complex and lightweight structures. Knowledge of the link between the L-PBF process parameters and the mechanical properties of final products have steadily increased over the past years. However, certification of L-PBF critical parts remains difficult in the aerospace sector, partly due to large variations in mechanical properties and fatigue behaviour. Complex L-PBF part geometries can severely influence local microstructure resulting in different mechanical properties throughout Ti6Al4V L-PBF components [1]. To benefit from the design freedom provided by the L-PBF process, the geometry-induced variations in microstructure and mechanical properties have to be predicted and ultimately negated without limiting the design space. To this end, the current study investigates a method for simulation-based process optimization to achieve a more homogeneous L-PBF process and thus L-PBF components with more predictable mechanical properties. In this study, macro-scale thermal simulation of the L-PBF process is employed to predict and limit geometry-induced overheating of complex Ti6Al4V components. First, the overheating effect is reproduced in tensile specimens. It is observed that overheating can cause an increase of oxygen pick-up during the L-PBF process. This is found to increase the local oxygen content by almost 80% and lower the elongation at break by over 70% in overheated regions. By employing macro-scale thermal simulations, an automated routine is developed to efficiently optimize the L-PBF process to prevent local overheating. Variable inter layer wait times are numerically optimized to allow cooling of the material without adding manufacturing time where this is not required. In this way, local overheating can successfully be prevented resulting in a more homogeneous temperature distribution during the L-PBF process. This method was found to fully restore the mechanical properties in geometries prone to overheating, resulting in more homogeneous and predictable Ti6Al4V components. Therefore, this method provides the possibility to widen the design space in L-PBF, as complex geometries can be more consistently manufactured and therefore better certified.