PSI - Issue 2_A

W. Reschetnik et al. / Procedia Structural Integrity 2 (2016) 3040–3048 W. Reschetnik et al. / Structural Integrity Procedia 00 (2016) 000–000

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suggests a ductile fracture behaviour. It confirms the results shown in Table 3 that the vertically built specimen showed more ductility comparing to other specimen conditions. Besides, non- melted particles were observed in this specimen. According to these findings, a relationship between non-melted particles, cracks and SLM process parameters are a major subject of a follow-up study. Table 3 compares the tensile results of the specimens manufactured by SLM and conventional methods. The vertically SLMed specimen shows a higher ultimate tensile strength and elongation to failure than the horizontally build specimen. It is assumed that different microstructures after the SLM process may be a reason for the improvement of the tensile strength. Moreover, microstructural evolution after SLM process will be detailed in the future work. 4. Conclusions The results of the current work show that gas atomized powder from the aluminium alloy EN AW-7075 can be used to manufacture complex structures by selective laser melting. This work shows that under the presented conditions additively build structures cannot be used for high performance applications due to the low ultimate tensile strength at low elongation as compared to conventionally manufactured parts. The fracture mechanical performance as well as the threshold values of the stress intensity factor are below the known material values for this aluminium alloy. The results of the tensile tests and the fatigue crack growth behaviour on as-built and heat treated specimens demonstrate an anisotropic behaviour related to the building direction. The reason for the low mechanical properties can be found by process-induced initial cracks parallel to the building direction. A relatively large range of solidification temperatures can be one explanation for this phenomenon. In order to improve the mechanical properties, additional investigation with different process parameters on the EN AW-7075 powder and possible post-treatments is essential. References Davis, J.R., 1996. Aluminium and aluminium alloys. 3rd edn. Materials Park, Ohio. DIN 50125. Testing of metallic materials – Tensile test pieces; E DIN 50125:2008-10. DIN EN 573-3. Aluminium and aluminium alloys - Chemical composition and form of wrought products - Part 3: Chemical composition and form of products; German version EN 573-3:2009. DIN EN 755-2. Aluminium and aluminium alloys - Extruded rod/bar, tube and profiles – Part 2: Mechanical properties; German version EN 755 2:2008. DIN EN ISO 6892-1. Metallic materials - tensile testing - part 1: method of test at room temperature; ISO 6892-1:2009. Eberlein, A., 2016. Einfluss von Mixed-Mode-Beanspruchung auf das Ermüdungsrisswachstum in Bauteilen und Strukturen. 1st edn., Universität Paderborn. FKM-Richtlinie, 2012. Rechnerischer Festigkeitsnachweis für Maschinenbauteile aus Stahl, Eisenguss- und Aluminiumwerkstoffen. 6th edn., VDMA-Verl., Frankfurt am Main. Gebhardt, A., 2013. Generative Fertigungsverfahren: Additive Manufacturing und 3D Drucken für Prototyping - Tooling - Produktion. 1st edn., Carl Hanser Fachbuchverlag, München. Gebhardt, A., 2014. 3D-Drucken: Grundlagen und Anwendungen des Additive Manufacturing (AM). Hanser, München. Gibson, I., Rosen, D.W., Stucker, B., 2010. Additive manufacturing technologies: Rapid prototyping to direct digital manufacturing. Springer, New York. Holt, R.T., Wallace, R., Wallace, W., DuQuesnay, D.L., 2000. RRA Heat Treatment of Large Al 7075-T6 Components. Defense Technical Information Center, Ft. Belvoir. Jackson, M.J., Ahmed, W., 2007. Surface engineered surgical tools and medical devices. Springer, New York. Leuders, S., Thöne, M., Riemer, A., Niendorf, T., Tröster, T., Richard, H. A., 2013. On the mechanical behaviour of titanium alloy TiAl6V4 manufactured by selective laser melting: Fatigue resistance and crack growth performance. International Journal of Fatigue 48, 300-307. Ostermann, F., 2014. Anwendungstechnologie Aluminium. 3rd edn., Springer Berlin Heidelberg, Berlin, Heidelberg. Richard, H. A., Sander, M., 2012. Ermüdungsrisse: Erkennen, sicher beurteilen, vermeiden. 3nd edn., Springer Vieweg, Wiesbaden. Riemer, A., Leuders, S., Thöne, M., Richard, H. A., Tröster, T., Niendorf, T, 2014. On the fatigue crack growth behavior in 316L stainless steel manufactured by selective laser melting. Engineering Fracture Mechanics 120, 15-25. Riemer, A., 2015. Einfluss von Werkstoff, Prozessführung und Wärmebehandlung auf das bruchmechanische Verhalten von Laserstrahlschmelzbauteilen. 1st edn., Shaker, Herzogenrath. Sander, M., Richard, H. A., 2004. Automatisierte Ermüdungsrissausbreitungsversuche. Materials Testing 46, 22-16. ASTM, 2008. Annual book of ASTM standards. Section 3: Metals test methods and analytical procedures, vol 03.01. Metals - Mechanical testing, elevated and low-temperature tests. Metallography, 2008: E 647-08.