https://popups.uliege.be/esaform21/index.php?id=2436 Index terms fr 0 https://popups.uliege.be/esaform21/index.php?id=1563 Despite the attractive capabilities of additive manufacturing (AM) technology, the industrialization of these processes remains very low. This is attributed to the complexes physical phenomena involved in the AM process and the layered structure of the produced parts. Intense research work is still needed for the prediction and optimization of AM parts mechanical properties. In this study, the influence of particle size distribution (PSD) of stainless steel 316L (SS 316L) powders on AM parts properties was investigated. Four PSD were used to produce test parts and compare the resulting porosity, surface roughness and macro-hardness. The SS 316L specimens were fabricated by Laser Powder Bed Fusion process (LPBF) on a SLM 125HL machine using variations in laser power and scan velocity. Computed scan tomography (CT) was used to characterize the defects. Lack of fusion and keyhole defects were detected. Defects were detected even in nearly dense parts. The powder size distribution was found to affect the porosity. Results from CT tests were used to identify the minimum achievable porosities for each powder, through the appropriate selection of process parameters. The macro-hardness and surface roughness were found to vary with the powder properties. Mon, 22 Mar 2021 20:12:13 +0100 Mon, 05 Apr 2021 18:14:24 +0200 https://popups.uliege.be/esaform21/index.php?id=1563 https://popups.uliege.be/esaform21/index.php?id=2464 Laser powder bed fusion (LPBF) is an additive manufacturing technique that is widely used to produce AlSi10Mg parts with a good strength-to-weight ratio and a very fine microstructure thanks to high cooling rates. However, to obtain better mechanical properties, a good ductility and higher fatigue resistance, post-treatments have to be performed. In this work, friction stir processing, a thermomechanical post-treatment, is applied on an as-built plate of 5 mm of thickness. This post-treatment leads to a decrease of the percentage of porosities and to modification of the microstructure: globularized Si-rich particles are surrounded by the α-Al phase. The method presented uses nanoindentation to determine the behavior of the different phases present in the material for future numerical simulations and a better understanding of the relation between microstructure and fatigue strength. The Bucaille method [1] is used to determine the links between indentation curves and elastoplastic parameters. Three different pyramidal indenters are used: Berkovich, cube corner and an indenter with a centerline-to-face angle of 50 degrees. From the loading / unloading curves and after post-processing, the Young's modulus, the representative strain and the associated stress are determined. With the three different indenters and their three true stress/true strain points, a good description of the elastoplastic behavior can be defined. Tue, 23 Mar 2021 19:28:40 +0100 Tue, 30 Mar 2021 09:33:34 +0200 https://popups.uliege.be/esaform21/index.php?id=2464 https://popups.uliege.be/esaform21/index.php?id=2433 Powder bed additive manufacturing allows for the production of fully customizable parts and is of great interest for industrial applications. However, the repeatability of the parts and the uniformity of the mechanical properties are still an issue. More specifically, the physical mechanism of the spreading process of the powders, which significantly affects the characteristics of the final part, is not completely understood. In powder bed fusion technologies, the spreading is performed by a device, typically a roller or a blade, that collects the powders from the feedstock and successively deposits them in a layer of several dozens of microns that is then processed with a laser beam. In this work, an experimental approach is developed and employed to study the powder spreading process and analyze in detail the motion of the powders from the accumulation zone to the deposition stage. The presented experiments are carried out on a home-made device that reproduces the spreading process and enables the measurement of the characteristics of the powder bed. Furthermore, the correlation with the process parameters, e.g., the speed of the spreading device, is also investigated. These results can be used to obtain useful insights on the optimal window for the process parameters. Tue, 23 Mar 2021 19:02:41 +0100 Mon, 29 Mar 2021 20:19:10 +0200 https://popups.uliege.be/esaform21/index.php?id=2433