Influence of the Manufacturing Parameters in Selective Laser Melting on Properties of Aluminum Alloy AlSi7Mg0.6 (A357) Arnold Mauduit * , Hervé Gransac, Sébastien Pillot CETIM Centre Val de Loire (CRAl: Centre de Référence de l’Aluminium – pôle matériaux et procédés), 3 – 7 rue Charles de Bange, Bourges 18000, France Corresponding Author Email: arnold.mauduit@cetimcentrevaldeloire.fr https://doi.org/10.18280/acsm.450101 ABSTRACT Received: 14 September 2020 Accepted: 18 January 2021 Various selective laser melting (SLM) configurations (8 in all) were tested on aluminum alloy AlSi7Mg0.6 by making single tracks on parallelepipeds specimens. We used an energy balance as a means of connecting the machine parameters (power, speed, etc.) of the 8 configurations to the morphology (geometry) of the single tracks. On this basis, we correlated the width, depth and especially the section area of the melt pool (single track) to the linear energy density. We were also able to assess the absorption coefficient of the aluminum alloy AlSi7Mg0.6 as a function of the temperature. The study was then focused on the microstructure and the possible impacts on the material properties including on the mechanical characteristics and the anisotropy observed in literature based on the build direction. Evidence suggests that the Hall-Petch relation can be used to explain this anisotropy. The thermal analysis highlighted two laser operating modes: the keyhole mode and the conduction mode. These modes have also been described via the morphology of the single tracks. Finally, a comparison between Rosenthal’s theoretical model (in the case of the conduction mode) and actual conditions was proposed by the obtained geometry of the single tracks as well as the cooling speeds calculated and measured using the dendrite arm spacing (DAS). The maximum temperatures achieved were also assessed by Rosenthal’s theoretical model which made it possible to explain the evaporation of some chemical elements during the manufacturing of the aluminum alloy through SLM. Keywords: selective laser melting, AlSi7Mg0.6 alloy (A357), manufacturing parameters 1. INTRODUCTION Selective laser melting (SLM), also called laser powder bed fusion (LPBF) is an additive manufacturing technique. It is characterized by layer-by-layer construction of a part to be produced: a laser melts the metal powder according to 3D data entered into a computer. This process is now well known and documented [1]. As opposed to conventional processes such as machining which are carried out by removing material, SLM has a direct impact on the properties of the material used given that the material is melted (liquid state). Therefore, the manufacturing parameters have a direct influence on the metallurgy of the material thus produced. Naturally, the initial aim of adjusting the manufacturing parameters is to obtain a material that is as dense as possible and which therefore has a low porosity rate. However, these parameters will also have a significant impact on the mechanical behavior of the material, its physical properties, as well as the surface condition. Many articles have been written on the optimization of manufacturing parameters to obtain a dense material [2-4] using in particular design of experiment methods. Additionally, these articles present the mechanical characteristics, the hardness, the metallurgy that these parameters have induced on the material. But, in general, this work only shows the impact of manufacturing parameters on the properties of the material. Some authors try to highlight correlations in their observations [5-7]. Unlike previous articles, we focus on one material: aluminum alloy AlSi7Mg0.6. As presented in the rest of the document, our work highlights the influence of the manufacturing parameters on the track produced, on its metallurgy and consequently on its physical and mechanical properties. We also sought to draw a correlation between the produced tracks and a thermal model of the SLM in the case of aluminum alloy AlSi7Mg0.6. 2. MATERIALS AND METHODS 2.1 SLM machine The SLM machine used for the study is a SLM 280 HL (made by SLM solutions) initially equipped with a 400 W power YAG laser (version 1.0) and modified with a 700 W YAG laser (version 1.5). The build platforms are made from aluminum alloy. The temperature of the build platform is 150°C. All the tests were carried out with a protective gas (argon with a minimum purity rate of 99.99%). The layer thickness was set to 50 μm. 2.2 Powder The aluminum alloy AlSi7Mg0.6 powder used during this study was supplied by TLS Technik. This batch has already been used for a previous study and presented in an earlier publication [8]. The main purpose of this document [8] is to Annales de Chimie - Science des Matériaux Vol. 45, No. 1, February, 2021, pp. 1-10 Journal homepage: http://iieta.org/journals/acsm 1