Effect of process parameters on the mechanical properties of a Titanium alloy fabricated by Electron Beam Melting (EBM)

Electron Beam Melting is a layer-by-layer additive manufacturing technique which proved to be very efficient and versatile in the fabrication of medical devices and automotive or aerospace components. Due to the highly innovative character of the technology, its potential is not yet fully exploited and a comprehensive understanding of how the different processing parameters may affect the mechanical performance of the resulting materials still deserves to be achieved. Tensile tests on a Titanium alloy (Ti-6Al-4V-ELI) are ran at static rates for investigating the effects of different fabrication parameters on the material response, namely the speed function, the line offset, the focus offset, the number of contours and the horizontal-vertical growing direction of the specimens. A combination of such parameters is identified as a “process setup” and different setups are adopted for producing corresponding series of specimens, machined after fabrication according to ASTM F2924 and ASTM E8 regulations. The experimental procedure relies on enhanced true stress-true strain data based on the optical measurement of the neck cross section of the specimen, as an alternative to the traditional elongation-based approach to the true stress-true strain evaluation. This approach allows to better highlight the effects of the different process setups on the material performance, by focusing on the most stressed/strained material points within the overall specimen volume. The true curves allow to relate the material performance in terms of both strength and ductility to each process setup, allowing to outline the influence of single/combined fabrication parameters on the two above performance indicators.