PSI - Issue 13

J.-P. Brüggemann et al. / Procedia Structural Integrity 13 (2018) 311–316 J.-P. Brüggemann et al. / Structural Integrity Procedia 00 (2018) 000 – 000

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1. Introduction

Additive manufacturing (AM) is a modern technology for manufacturing complex components and structures, Gibson et al. (2010). Due to the layer-wise manufacturing, ready-to-use, lightweight-optimized products can be directly generated on the basis of 3D-CAD data without forming tools, Gebhardt (2013). During the SLM manufacturing process, the steps of coating, irradiation and lowering are repeated. As a result, the component is built up layer by layer until completion, see Fig. 1.

Fig. 1. SLM-process, Brüggemann et al. (2016).

Typical areas of application for AM components are aerospace, medical technology and the automotive industry. Used materials for the AM process are both plastics and metallic materials, Wohlers and Caffrey (2015). In order to meet the high demands of these industries, high-quality products must be produced. Selective laser melting (SLM) enables the production of nearly 100% dense metallic components, Leuders et al. (2013), which can be subjected to high levels of mechanical and thermal stress. This technology also offers the possibility of producing complex structures, such as undercuts, lattice structures or topology-optimized components, Riemer (2015). A typical material used in the SLM process is the titanium alloy Ti-6Al-4V, due to its high mechanical properties and biocompatibility, Jackson and Ahmed (2007). In the industrial sector, the concept of lightweight construction is increasingly coming to the fore against the backdrop of resource conservation and the associated reduction in emissions. Particularly in aerospace, materials with low density and good mechanical properties such as aluminum alloys are of particular interest. Experience from conventional manufacturing shows a good performance of the high-strength aluminum alloy EN AW-7075. Scientific investigations, Reschetnik et al. (2016) and Skalický et al. (2017), on the processability of this alloy in the SLM process shows that prepared samples have anisotropic behavior due to process-induced hot cracks. Furthermore, it was not possible to determine solid results regarding the fracture mechanical characterization. Due to its chemical composition, aluminum alloy EN AW-7075 has a high solidification interval, Mondolfo (1976). As a result, the melting and solidification of the material results in a high affinity for the formation of hot cracks, Earle et al. (2004). An investigation by Montero-Sistigia et al. (2016) shows that addition of 4 Wt.-% silicon avoids hot cracking. This is due to a reduction of the thermal expansion coefficient. Furthermore, another investigation shows that an increase of the pre-heating temperature of the building platform reduces the number of hot cracks, Brüggemann et al. (2017). In practice, pure silicon is not always available for the modification of the powder, which is why a practice-oriented approach to the production of a mixed alloy made of high-strength EN AW-7075 and silica-rich AlSi10Mg is pursued in the context of this study.

2. Experimental details

In the present research a mixed aluminum alloy is manufactured with a drum hoop mixer by mixing 50 Wt.-% EN AW-7075 alloy and 50 Wt.-% AlSi10Mg. To analyze particle size and shape of the new mixed aluminum alloy