SIGNIFICANCE OF INTRA-BUILD DESIGN VARIABLES ON THE FRACTURE TOUGHNESS PROPERTIES OF ELECTRON BEAM MELTED TI6AL4V

Structurally reliable materials are essential for adopting additive manufacturing (AM) metals in safety-critical applications. Limited data on the damage-tolerance properties of metal AM materials exists, hindering the acceptance of AM metals in fracture-critical applications. A design of experiments (DOE) is used in this study to investigate the role of build space and part design parameters on the fracture toughness properties of Electron Beam Melted (EBM) Ti6Al4V. ASTM E399 tests were performed on over 100 compact tension (CT) samples in the as-built and machined conditions to obtain fracture toughness properties and evaluate the influence of part size and location within 80% of the build space. Results were comparable to wrought annealed titanium, with less than 10% variation in overall fracture toughness. Specimen location within the build envelope contributed to the observed variation, with an increase in properties with build height and specimens located in the center of the build envelope. The location-dependent properties result from changes in microstructure and porosity throughout the build space. While the experimental EBM Ti6Al4V fracture toughness properties are promising for future applications, it is crucial to consider the variation in properties due to build space location and design parameters when designing for consistency.
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