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Before utilising selective laser melting in real applications, the process as well as the outcome component and its characteristics need to be fully understood. Based on the layer-wise fabrication, with its distinctive orientations in translations and thermal influences within this additive manufacturing process, the obtained material properties and the microstructure are anticipated to be anisotropic. The selective laser melting process involves: the laser movement pattern in plane and rotation between single layers; recoater movement; substrate plate heating and movement; laser irradiation from the top; and inert gas flow. In order to gain insight into the process and its related characteristics, different sets of prismatic specimens in terms of orientation and inclination were produced and evaluated. The evaluation contained surface quality investigations with two independent measurement approaches, i.e. tactile and optical, density measurements based on the Archimedes principle and micro-section evaluation. Furthermore, ultrasonic analyses were conducted to study the feasibility of determining the mechanical properties, i.e. Young's modulus and Poisson's ratio, in accordance with the recorded longitudinal and transversal sonic velocities.The chosen raw material for these investigations was AlSi10Mg and the fabricated parts exhibited a high relative density of at least 99.5 %. Remarkable deviations were evident in the obtained surface quality and clear trends could be determined based on the inclination and orientation condition of the sample during manufacturing. In regards to the ultrasonic investigation, it was found that the reported inherent anisotropy of selective laser melted samples could not be detected with the non-destructive ultrasonic investigation, and destructive procedures, to date, represent the only reliable method to accurately reveal the material characteristics.Keywords: Powder-bed based additive manufacturing / Flushing process / irradiation strategy / Positioning and inclination / Surface quality Im Rahmen der erfolgreichen Implementierung des selektiven Laserstrahlschmelzens in industriellen Anwendungen sind die Kenntnis und das Verständnis der charakteristischen und verfahrensbezogenen Eigenschaften der generierten Kompo-

Additive manufacturing represents a unique opportunity for the generation of highly complex components. Given the inherent anisotropic material behaviour, reasoned in the layer-wise generation process and the resulting span of mechanical properties with the lack of available data, the implementation of this manufacturing technique in industrial applications is challenging and requests expensive and time consuming material testing. This work focuses on the fracture toughness of selective laser melted precipitation-hardenable AlSi10Mg specimens, including positioning and inclination effects. Samples in accordance to the ASTM E 399-08 standard were fabricated in six different orientations and were subject to mode I fracture toughness testing. The notches were implemented in a subsequent milling procedure and the evaluation was undertaken as outlined in the ASTM E 1820-09 standard. Minor directional dependencies were found and the selective laser melted samples revealed similar fracture toughness results as conventional bulk material, namely K IC-values in the range from 40 to 60 MPa√m.

Selective laser melting is gaining importance to manufacture reliable and highly complex parts. However, the surfaces of the selective laser melted parts exhibit for many applications an insufficient high roughness, thus require subsequent post processing steps. A relatively new way to reduce the surface roughness is the laser polishing technique. In the present paper, additively manufactured AlSi10Mg samples were polished with different laser intensities and laser modes. The investigations contain the potential of roughness reduction and enhancement of the surface appearances, which can be achieved by laser polishing of the as‐built surfaces. An initial arithmetic mean roughness of 8.43 μm was remarkably reduced up to 98 %. The compositions of the polished surfaces were detected and the surface appearances were examined. Reasons and mechanisms were explained and depicted for the occurred shade formations on the polished surfaces. High laser intensity led to segregation of silicon and magnesium on the surface. A higher laser intensity enabled an increased melt depth within the conture layer of the selective laser melting structure. Through increasing melt depth, a porosity of max. 1.7 % was detected in the remolten area. Hardness investigations of the initial and laser remolten cross section revealed no significant reduction in hardness.

Laser powder bed fusion is a well‐established 3D printing technique for metal alloys, but exhibits a poor surface quality. Laser polishing provides the possibility of a fast contact‐free and fully‐automatable surface treatment. This paper deals with the experimental investigation of laser polishing of laser powder bed fusion parts made of aluminium AlSi10Mg. Laser polishing is done with a 4 kW solid state disc laser in combination with a multi‐axis system and a one dimensional scanner optic. The laser is operated at continuous and pulsed operation mode. The parameter study reveals a high dependency of the achievable roughness on the laser beam intensity, the track and pulse overlap, the energy density and the number of polishing passes and polishing directions. Pulsed laser polishing mode with up to four passes from different directions revealed the lowest surface roughness of 0.14 μm Ra. With respect to the initial average surface roughness of Ra = 8.03 μm a reduction of the surface roughness of greater than 98 % could be achieved. Polishing with continuous laser radiation at one polishing pass resulted in Ra = 0.23 μm at an area rate of 20 cm2/min. Laser polishing using four passes achieved a further improvement up to Ra = 0.14 μm.