Geometry Effect on Microstructure and Mechanical Properties in Laser Powder Bed Fusion of Ti-6Al-4V

Metals, vol. 12, pp. 482

Abstract

Laser Powder Bed Fusion (LPBF) of Ti-6Al-4V enables the manufacturing of complex parts for lightweight applications. The emerging microstructure in the LPBF process and thus the mechanical properties are defined by the thermal cycles, which are locally variable for complex geometries. Predictions of local mechanical properties by simulation would reduce the development time of new applications drastically but are today not possible on part scale, so new part applications must be qualified experimentally at great effort. In this study, representative geometry sections were transferred into a simplified sample shape to mechanically characterize different geometry-dependent microstructures. In areas exposed to comparatively increased heat input over time, a lamellar α + β microstructure with β fraction up to 20% was measured in contrast to the common martensitic α′ microstructure of LPBF-manufactured Ti-6Al-4V, resulting in reduced tensile strength and fatigue life. For the first time, a correlation was successfully established between ultimate tensile strength of multiple geometries and the corresponding temperature–time cycles. With reduced computational effort by use of simplifying assumptions in the simulation, this correlation model can theoretically be applied to the part level. This work has laid the foundation for the simulation-based prediction of mechanical properties for entire parts manufactured with LPBF.

Authors 5

1. Juri Munk corresponding Aachen Fraunhofer Institute for Laser Technology ILT

   Fraunhofer Institute for Laser Technology

   Affiliation as printed

   Fraunhofer Institute for Laser Technology ILT, Steinbachstraße 15, 52074 Aachen, Germany

2. Eric Breitbarth

   Deutsches Zentrum für Luft- und Raumfahrt e. V. (DLR)

   Affiliation as printed

   Institute of Materials Research, German Aerospace Center (DLR), Linder Höhe, 51147 Cologne, Germany

3. Tobias Siemer Aachen Fraunhofer Institute for Laser Technology ILT

   Fraunhofer Institute for Laser Technology

   Affiliation as printed

   Fraunhofer Institute for Laser Technology ILT, Steinbachstraße 15, 52074 Aachen, Germany

4. Norbert Pirch Aachen Fraunhofer Institute for Laser Technology ILT

   Fraunhofer Institute for Laser Technology

   Affiliation as printed

   Fraunhofer Institute for Laser Technology ILT, Steinbachstraße 15, 52074 Aachen, Germany

5. C. Haefner Aachen Chair for Laser Technology LLT Fraunhofer Institute for Laser Technology ILT

   Fraunhofer Institute for Laser Technology · RWTH Aachen University

   Affiliation as printed

   Chair for Laser Technology LLT, RWTH Aachen University, Steinbachstraße 15, 52074 Aachen, Germany

   Fraunhofer Institute for Laser Technology ILT, Steinbachstraße 15, 52074 Aachen, Germany