PSI - Issue 24

Giulia Morettini et al. / Procedia Structural Integrity 24 (2019) 349–359 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

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test. Only from a comparative analysis with stress relieved specimen (applying a proper post heat treatment) will be possible to outline an exhaustive picture of the situation.

Conclusion and future prospect

In conclusion the present paper shows that in as-built condition, Ti-6Al-4V specimens produced by DMLS technique show a significant anisotropy of the material in fatigue proprieties was detected. In particular, the vertical specimens have a fatigue limit 30 MPa lower than the horizontal counterpart. From the previous discussions, it is possible to affirm that the key studied parameters (i.e. surface roughness and residual stress) have an interactive effect on the overall fatigue behaviour of the specimens. With higher surface roughness of horizontal specimens, lower fatigue resistance is expected, however, significantly higher residual stress in this part possibly overcomes the effect of surface roughness, increasing its fatigue resistance. Definitely a future investigation of the microstructures of the material and research of presence of defects or the effects of phase and grain size on the fatigue proprieties is necessary. In the near future the Authors will investigate therefore these aspects in order to also analyse their influence in fatigue behaviour of the vertical and horizontal specimens. In a later step, instead, we will proceed to carry individually out all the improvement processes listed Reza (2018) (surface treatments, heat treatments, etc.) and the influence of a notch Razavi (2018) in order to verify their independent effect on the fatigue behaviour of the specimens tested. Bača A., Konečná R., Nicoletto G., Kunz L., 2016. Influence of build direction on the fatigue behaviour of Ti6Al4V alloy produced by direct metal laser sintering. Materials Today: Proceedings 3, 921-924. Benedetti M., Fontanari V., Bandini M., Zanini F., Carmignato S., 2018. Low- and high-cycle fatigue resistance of Ti-6Al-4V ELI additively manufactured via selective laser melting: Mean stress and defect sensitivity. International Journal of Fatigue 107, 96-109. 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