PSI - Issue 28

Daniel Kotzem et al. / Procedia Structural Integrity 28 (2020) 11–18 Daniel Kotzem et al. / Structural Integrity Procedia 00 (2019) 000–000

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4. Conclusions and outlook Within the scope of this work, the damage tolerance within a single unit cell plane was investigated for the f 2 ccz lattice type based on the E-PBF manufactured Ti6Al4V alloy. The microstructure of the E-PBF manufactured specimens consists of a mixture of α + β structure, combined with acicular α’ martensite phases. Through µ-CT analysis it could be demonstrated that near fully-dense components can be manufactured by E-PBF. Within cyclic testing, measurement techniques such as DIC and thermography can be qualified for the reliable detection of partial failure within the specimen. In particular, failure within the specimen can be identified by a local temperature increase due to dissipated energy. Furthermore, DIC data can be used to compile stress-strain hysteresis loops. It could be stated that the increasing damage progress leads to stiffness degradation especially under tension, resulting in a buckling of the hysteresis loop. In comparison to the reference material, similar cyclic properties can be noticed in the LCF range. However, with increasing number of cycles higher variances are present which might be attributed to local stress concentrations, resulting from the process-induced surface topography of the E-PBF manufactured specimens. Future investigations will focus on the adaption of the presented measurement techniques towards complex lattice structures which consist of several linked unit cells in order to describe and evaluate the different damage mechanisms under cyclic loading. Furthermore, it has to be proved how the increasing complexity of the component affects the damage tolerance. Acknowledgements Authors would like to thank the German Research Foundation (Deutsche Forschungsgemeinschaft, DFG) for its financial support within the research project No. 379213719 “Damage tolerance evaluation of electron beam melted cellular structures by advanced characterization techniques” (NI 1327/13-1, WA 1672/32-1). Furthermore, authors would like to thank Thomas Niendorf and Tizian Arold (University of Kassel) for providing the investigated material in the framework of an excellent collaboration. References Basquin, O. H. (1910). The exponential law of endurance tests. Proceedings ASTM 10 , 625–630. Brenne, F., Niendorf, T., & Maier, H. J. (2013). Additively manufactured cellular structures: Impact of microstructure and local strains on the monotonic and cyclic behavior under uniaxial and bending load. Journal of Materials Processing Technology , 213 (9), 1558–1564. Chan, K. S. (2015). Characterization and analysis of surface notches on Ti-alloy plates fabricated by additive manufacturing techniques. Surface Topography: Metrology and Properties , 3 (4), 44006. Heinl, P., Müller, L., Körner, C., Singer, R. F., & Müller, F. A. (2008). Cellular Ti-6Al-4V structures with interconnected macro porosity for bone implants fabricated by selective electron beam melting. Acta biomaterialia , 4 (5), 1536–1544. Herzog, D., Seyda, V., Wycisk, E., & Emmelmann, C. (2016). Additive manufacturing of metals. Acta Materialia , 117 , 371–392. Kahlin, M., Ansell, H., & Moverare, J. J. (2017). Fatigue behaviour of notched additive manufactured Ti6Al4V with as-built surfaces. International Journal of Fatigue , 101 , 51–60. Koike, M., Greer, P., Owen, K., Lilly, G., Murr, L. E., Gaytan, S. M., Martinez, E., & Okabe, T. (2011). Evaluation of titanium alloys fabricated using rapid prototyping technologies-electron beam melting and laser beam melting. Materials (Basel, Switzerland) , 4 (10), 1776–1792. Körner, C. (2016). Additive manufacturing of metallic components by selective electron beam melting — a review. International Materials Reviews , 61 (5), 361–377. Kotzem, D., Arold, T., Niendorf, T., & Walther, F. (2020). Damage tolerance evaluation of E-PBF-manufactured Inconel 718 strut geometries by advanced characterization techniques. Materials , 13 (1), 247. Liu, S., & Shin, Y. C. (2019). Additive manufacturing of Ti6Al4V alloy: A review. Materials & Design , 164 , 107552. Persenot, T., Buffiere, J.-Y., Maire, E., Dendievel, R., & Martin, G. (2017). Fatigue properties of EBM as-built and chemically etched thin parts. Procedia Structural Integrity , 7 , 158–165. Radaj, D., & Vormwald, M. (2007). Ermüdungsfestigkeit: Grundlagen für Ingenieure. (3th edition). Berlin, Heidelberg: Springer-Verlag. Walther, F., & Eifler, D. (2007). Cyclic deformation behavior of steels and light-metal alloys. Materials Science and Engineering: A , 468-470 , 259–266. Wauthle, R., Vrancken, B., Beynaerts, B., Jorissen, K., Schrooten, J., Kruth, J.-P., & van Humbeeck, J. (2015). Effects of build orientation and heat treatment on the microstructure and mechanical properties of selective laser melted Ti6Al4V lattice structures. Additive Manufacturing , 5 , 77–84.