PSI - Issue 53

Stefania Franchitti et al. / Procedia Structural Integrity 53 (2024) 397–406 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

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characterization tests: chemical composition, particle size distribution, porosity, apparent density, tapped density, flow rate and morphology. 3.3. Verification phase at sample level In order to define the intrinsic material properties of the Ti6Al4V processed by EBM an intensive test campaign was performed: • Metallography Analysis : such analysis has been performed on bars. Microstructural analyses were performed on Ti6Al4V samples made with the EBM process. The samples were obtained from 6 cylindrical bars of different diameters that were cut both transversely (samples with a circular section) and longitudinally (samples with a rectangular section). After cutting, the samples were encapsulated, lapped and etched in order to observe their microstructure under a microscope. Further detail about the analysis can be found in Silvestri et al. (2020). • Tensile Test: In order to determine the mechanical behaviour of the Ti6Al4V processed by EBM technology, an extensive static tensile test campaign was performed on different families of specimens, each consisting of at least 5 specimens to obtain a sample of statistical value. The different families of specimens have allowed us to assess the influence of: • Fatigue Test: In order to determine the fatigue resistance of the Ti6Al4V material processed with EBM technology, 3 test campaigns were performed on three different types of samples: 1) As built samples; 2) Machined specimens; 3) Machined and hipped specimens For each test campaign, n.30 specimens were produced for a total of 90 specimens. The n.30 specimens of each family were tested at n.6 load levels (n.5 specimens for each load level). The Wohler curves for each of the n.3 families were determined using the following test execution parameters: (R = 0.1, Kt = 1 and load frequency=87 Hz). Further details about the fatigue test campaign can be found in Franchitti et al. (2020). • X-ray CT analysis : In order to evaluate the distribution and characteristics of the defects generated during the EBM process, a tomographic analysis was performed on a batch of n. 60 specimens in the shape of a parallelepiped 10 x 10 x 50 mm made of Ti6Al4V by using EBM technology. In order to assess the influence of both the position in the build volume and the growth orientation on the characteristics of the defects generated, the specimens were built in: - Four different orientations (along X axis, along the Y axis, at 90 ° and at 45 ° with respect to the start plate positioned on the mobile platform) - Five different zones (one in the center of the building chamber, while the others at the corners) - Three different heights. Further details on the CT analysis can be found in Pirozzi et al. (2019). • Fracture Test : Fracture toughness tests were carried out on n.6 CT specimens obtained starting from blocks of Ti6Al4V made of EBM which were subsequently processed by machining (external surface) 1) thickness of the layer (50  m vs. 100  m) 2) surface finishing status (as built vs. machined) 3) hipping heat treatment (hipped vs. not hipped) 4) size of the specimen (small vs. medium vs. standard size) 5) specimen shape (circular vs. rectangular section) 6) test temperature (-150 ° C, room temperature, 190 ° C, 300 ° C, 500 ° C, 700 ° C). Further detail about the tensile test campaign can be found in Pirozzi et al. (2017).