The AlSi10Mg alloy was processed by selective laser melting using both hot- and cold-build platforms. The investigation was aimed at defining suitable platform pre-heating and post-process thermal treatment strategies, taking into consideration the peculiar microstructures generated. Microstructural analyses, differential scanning calorimetry, and high-resolution diffraction from synchrotron radiation, showed that in the cold platform as-built condition, the amount of supersaturated Si was higher than in hot platform samples. The best hardness and tensile performance were achieved upon direct aging from cold platform-printed alloys. The hot platform strategy led to a loss in the aging response, since the long processing times spent at high temperature induced a substantial overaging effect, already in the as-built samples. Finally, the standard T6 temper consisting of post-process solution annealing followed by artificial aging, resulted in higher ductility but lower mechanical strength.

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The fatigue behaviour of an AlSi10Mg alloy processed by laser powder bed fusion (L-PBF) and subjected to different surface finishing processes was investigated paying special attention to the residual defects on the surface and the dominant fatigue failure mechanisms. Roughness measurements and qualitative surface morphology analysis showed smooth surfaces in the case of vibro-finishing and machining followed by polishing. The fatigue performance did not reveal to be directly related to surface roughness, but residual intrusions left on the finished surfaces. Post-mortem analysis showed single- or multiple-crack nucleation from pores opened on the surface, un-melted powders, or spatters considered as typical L-PBF defects. A fatigue limit of 195 MPa for machined and polished samples was obtained by substantial removal of surface and subsurface defects.

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Fatigue is the most common cause of failure of mechanical parts in engineering applications. In the current work, we investigate the fatigue life of a bulk metallic (BMG) glass fabricated via additive manufacturing. Specimens fabricated via laser powder-bed fusion (LPBF) are shown to have a fatigue ratio of 0.20 (fatigue limit of 175 MPa) in a three-point bending fatigue test. Three strategies for improving the fatigue behavior were tested, namely (1) relaxation heat treatment, giving a slight fatigue life improvement at high loading conditions (≥250 MPa), (2) laser shock peening, and (3) changing the build orientation, the latter two of which yielded no significant effects. It was found that the presence of lack of fusion (LoF) had the preponderant effect on fatigue resistance of the specimens manufactured. LoF was observed to be a source of stress localization and initiation of cracks. The fatigue life in BMGs fabricated by LPBF is thus primarily influenced by powder quality and process-induced defects, which cannot be removed by the post-treatments carried out in this study. It is believed that a slight increase in laser power, either in the near-surface regions or in the core of the specimens, could improve the fatigue behavior despite the associated (detrimental) increase of crystallized fraction.

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In the present work, both the surface chemical contamination and the mechanical alteration of Ti–6Al–4V (Ti64) and Ti–6Al–4V extra low interstitial (Ti64ELI) titanium alloys subjected to superplastic forming (SPF) for the manufacturing of highly customized biomedical prostheses have been investigated. As case study, a cranial implant was considered. The design of the manufacturing process was assisted by a numerical model calibrated on free inflation experimental tests. Glow discharge optical emission spectrometry (GDOES) analyses, nanoindentation tests, and metallographic analyses allowed to relate the mechanical alteration to the oxygen enrichment due to the environmental exposition during processing. While similar diffusion kinetics were found, different oxidation rates were measured in the two investigated alloys. The hardness variation was strictly related to the oxygen content. In order to verify the material biocompatibility, cytotoxicity tests were conducted on the most oxidized part. Results highlighted that the oxygen enrichment due to the manufacturing process did not significantly affect the cells viability.