A comparative study of the effects of thermal treatments on AlSi10Mg produced by laser powder bed fusion Elisa Padovano a, * , Claudio Badini a , Anna Pantarelli a , Flavia Gili b , Fabio D’Aiuto b a Politecnico di Torino, Department of Applied Science and Technology, Corso Duca Degli Abruzzi 24,10129, Torino, Italy b Centro Ricerche FIAT, Group Materials Lab-Metals, Corso Settembrini 40, Torino, Italy article info Article history: Received 15 January 2020 Received in revised form 13 March 2020 Accepted 16 March 2020 Available online 20 March 2020 Keywords: Laser processing Mechanical properties Microstructure Metallography abstract The components produced by laser powder bed fusion (LPBF) generally require specific heat treatments in order to release the residual stresses induced during the additive manufacturing process. Post- processing treatments also play a significant role in obtaining components whose microstructure and characteristics are homogeneous and tailored for specific applications. A comparison of the mechanical features resulting from different heat treatments requires that a material showing the same initial mechanical features and microstructure is investigated. In the present work the effects of a number of different thermal post-processing treatments are compared: AlSi10Mg parts processed by LPBF under- went various thermal treatments such as stress relieving, annealing at high temperature and T6 treat- ments. The microstructure variation as a function of the applied temperature was correlated to the material mechanical behaviour in term of hardness and tensile strength; impact properties were also evaluated. The thermal evolution of the system was then studied through differential scanning calo- rimetry and x-ray diffraction analyses. © 2020 Elsevier B.V. All rights reserved. 1. Introduction Additive manufacturing (AM) techniques have attracted increasing interest in the scientific community due to the possibility of using a layer-by-layer strategy to produce near full-density com- ponents with complex geometries. In addition to the advantage of design freedom, this technology saves material and avoids the pro- duction of scraps and waste. Different metal AM technologies are currently available and find applications in many fields such as automotive, aerospace, orthopaedic implants etc. [1e4]. Among these technologies, Laser powder Bed Fusion (LPBF), also known as selective laser melting (SLM) is currently one of the most studied. LPBF is a powder bed fusion process that uses a laser source to selectively melt regions of deposited powder layers, according to a computer aided design (CAD) project. One of the most interesting aspects of this process is that it provides a very fine microstructure compared to that obtained using more conventional processing methods. Moreover, it is well known that this particular micro- structure greatly influences the mechanical behaviour of the mate- rial. LPBF can be applied to different metallic powders such as aluminium alloys, titanium, stainless steel and nickel. Aluminium alloys are the second most used metals, after steels. For this reason, the production of Al components through the LPBF process obtains low cost and high-quality parts for many different applications. Very commonly used aluminium alloys are those based on the AleSi system, as they are characterized by good castability, specific strength and good corrosion resistance [5e9]. In this context, the hypoeutectic AlSi10Mg alloy is frequently used in both foundry and additive manufacturing technologies; the great interest in this alloy is moreover confirmed by many scientific papers available in the literature. The components produced by metal additive manufacturing generally need specific heat treatments aimed at releasing the re- sidual stresses coming from the production process. Different kinds of residual stresses (RS) can in fact be present in as-built sample. According to Bartlett et al. [10], they can be classified on the base on the length scale they operate. Macroscopic RS act on the scale of the component geometry and can cause distortion phenomena; they are the most discussed in the literature due to the strong effects they have on mechanical properties of the as-built material. In addition, local stresses which act on individual grain scale or atomic scale stresses can also be present; however, they are only rarely investigated because of the difficulty to measure them. The stressed * Corresponding author. E-mail address: elisa.padovano@polito.it (E. Padovano). Contents lists available at ScienceDirect Journal of Alloys and Compounds journal homepage: http://www.elsevier.com/locate/jalcom https://doi.org/10.1016/j.jallcom.2020.154822 0925-8388/© 2020 Elsevier B.V. All rights reserved. Journal of Alloys and Compounds 831 (2020) 154822