PSI - Issue 42

Radomila Konecna et al. / Procedia Structural Integrity 42 (2022) 857–862 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

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cracks, and last but not least, due to high tensile residual stresses in the building direction co-acting with the applied cyclic stress. The fatigue life of specimens with A+ oriented notch which is lower than the best case B can be explained by the layer of nearly 400  m thickness having the specific microstructure due to hatching and contour and to stair stepping, Fig. 3. The residual stresses in the building plane are instead negligible. The difference in the fatigue life of notches with A+ and A- orientation can be qualitatively explained by the strong effect of the surface quality, i.e. orientation A- is a down skin surface with sharp surface irregularities (i.e. micronotches). In addition, there is the contribution of the microstructure, that is fine grained in the orientation A+ and coarse grained in the orientation A-. 5. Conclusions The orientation of the semi-circular notch with respect to the build direction has a large effect on fatigue life of as built L-PBF AlSi10Mg alloy in the high cycle fatigue region. For the orientation B (the notch root oriented in the building direction), the fatigue life for 2 x 10 6 cycles corresponds to the loading with maximum stress of 206 MPa, whereas for the notch orientation A- the corresponding maximum stress for the same life is 97 MPa, which makes only 47 % of the value for the orientation B. Fatigue life for orientation C is practically identical with the A- orientation. The fatigue life for A+ orientation lies nearly in the middle between extremes given by B and A-. A modified relative ranking of the notch orientation effect on fatigue in line with the observed surface quality of the as-built notches is however then determined by quantifying the important contribution of residual stresses and microstructure in the notch root: B is best in terms of fatigue strength, C is 17 % lower than B, A+ is 30 % lower than B and A- is 58 % lower than B. Acknowledgements The authors acknowledge the company BEAM-IT srl, Fornovo Taro, Italy for providing the specimens and the VEGA grant agency for the support by the grant No. 1/0463/19. References Beretta S., M. Gargourimotlagh, S. Foletti, A. du Plessis, M. Riccio (2020). Fatigue strength assessment of “as built” AlSi10Mg manufactured by SLM with different build orientations. International Journal of Fatigue 139 - 105737 Brandão, A.D., Gumpinger, J., Gschweitel, M., Seyfert, Ch., Hofbauer, P., Ghidini, T., 2017. Fatigue properties of additively manufactures AlSi10Mg – surface treatment effect. Procedia Structural Integrity 7, 58-66. Di Giovanni, M.T., Menezes, J.T.O., Bolelli, G., Cerri, E., Castrodeza, E.M., 2019. Fatigue crack growth behaviour of a selective laser melted AlSi10Mg. Enginering Fracture Mechnics 217, 106564. Larrosa, N.O., Wang, W., Read, N., Loretto, M.H., Evans, C., Carr, J., Tradowsky, U., Attallah, M.M., Withers, P.J., (2018). Linking microstructure and processing defects to mechanical properties of selectively laser melted AlSi10Mg alloy. Theoretical and Applied Fracture Mechanics 98, 123-133. Nicoletto, G., 2017. Anisotropic high cycle fatigue behavior of Ti – 6Al – 4V obtained by powder bed laser fusion. International Journal of Fatigue 94, 255-262. Nicoletto, G., 2020. Influence of rough as-built surfaces on smooth and notched fatigue behaviour of L-PBF AlSi10Mg. Additive Manufacturing 34, 101251. Nicoletto G., Daviddi D., Fornaci A. (2019) Simulation of residual stresses due to SLM fabrication and correlation with directional fatigue behavior of AlSi10Mg. II International Conference on Simulation for Additive Manufacturing". CIMNE, p. 91-98. Piette, T.D., Warren, R.J., Spangenberger, A.G., Hummelt, E.J., Lados, D.A., 2021. Microstructure evolution, fatigue crack growth, and ultrasonic fatigue in as-fabricated laser powder bed and conventionally cast Al-10Si-0.4Mg: A mechanistic understanding and integrated flaw-sensitive fatigue design methods. Material Science & Engineering A 825, 141892. Trevisan, F., Calignano, F., Lorusso, M., Pakkanen, J., Aversa, A., Ambrosio, E.P., Lombardi, M., Fino, P., Manfredi, D., 2017. On the selective laser melting (SLM) of the AlSi10Mg alloy: Process, microstructure, and mechanical properties. Materials 10 (1), 76. Zhang, J., Song, B., Wei, Q., Bourell, D., Shi, Y., 2019. A review of selective laser melting of aluminium alloys: Processing, microstructure, property and developing trends. Journal of Materials Science & Technology 35, 270-284. Zhao, L., Song, L., Macías, J.G.S., Zhu, Y., Huang, M., Simar, A., Li, Z., 2022. Review on the correlation between microstructure and mechanical performance for laser powder bed fusion AlSi10Mg. Additive Manufacturing 56, 102914.