LPBF manufacturing of Random Porous AlSi10Mg : relation process - structure - mechanical properties

Architected materials have experienced significant transformation recently due to the advent of additive manufacturing (AM), which allows for the creation of complex designs previously unattainable through conventional manufacturing. Metallic architected materials are particularly noteworthy because they combine the advantageous properties of metallic base materials with a lightweight design. This unique combination enables innovative developments across various fields, including energy, transportation, and healthcare. Today, these metallic architectures have been produced from various alloys using mainly powder bed fusion (PBF) processes, using either a laser or an electron beam as a heat source. However, manufacturing complex small-scale structures in metal poses significant challenges due to various phenomena occurring at different scales during the process. Indeed, research on metallic architected materials has revealed significant discrepancies between the actual properties observed and those predicted based on the initial design and base material. This issue is especially pronounced in periodic structures, which have shown a notable decline in performance compared to initial expectations. However, there is a lack of comprehensive data regarding non-periodic structures. This thesis explores an innovative form of disordered architecture using LPBF manufacturing. The materials feature through-thickness pores that are randomly dispersed within an AlSi10Mg matrix. The LPBF manufacturing of these complex structures and its impact on their structural and mechanical properties is the focus of this work. The structural investigation uses image processing for mesostructure analysis and Scanning Electron Microscopy (SEM) for microstructure characterization. Elastic properties are assessed through experimental methods, including nanohardness, tensile, and compression tests, as well as numerical analysis using Finite Element (FE) models. The impact of the process parameters on the defects at different scales is investigated. Among them, the contour scanning strategy proves to be particularly crucial. A representative FE model of the as-manufactured structures is created to analyze their elastic properties. Both experimental and numerical investigations show that the structures remain resilient to geometrical defects, maintaining a density-property relationship consistent with the Hashin-Shtrikman upper bound. Moreover, these imperfect structures retain their in-plane isotropy, despite variations in pore geometry.This work provides insights and tools regarding how the manufacturing process influences the properties of small-scale complex-shaped parts. The findings suggest that disordered structures are more resilient to defects than periodic ones, underlining the need for further research on non-periodic structures.