28 Juin – Thesis defense - Cassiopée Galy

11 h Amphi HSE - IUT Bordeaux (Gradignan)

Study of the material / process interaction in order to optimize the operating conditions of the SLM additive manufacturing process apply to aluminum alloys.

Interest in selective laser melting (SLM) has been growing in recent years, particularly with regard to the production of metal parts. The low density of aluminum alloys, combined with the possible design optimization enabled by additive manufacturing processes, ensures a significant decrease in the mass of structures which is very interesting for manufacturers in the automotive and aerospace industries. However, it is difficult to control the final properties of aluminum parts manufactured by SLM because many defects, such as porosity, hot cracking, and surface roughness, are generated during the process. To better understand how to optimize the performance of SLM aluminium parts, several studies were conducted during this work:
• An identification and selection of characterization methods well-adapted to the specificities of metallic materials developed by powder bed additive manufacturing processes was established. For instance, the comparison of different methods of determining the relative density of parts showed the advantages and disadvantages of each of the techniques;
• A study of the SLM machine highlighted the influence of various factors (gas flow, positions of specimens on the construction plate, or methods of depositing the powder) on the final properties of the produced parts. These elements have an impact on the density of the parts, their surface properties, and their mechanical properties. We found that the positioning of a piece on the tray is a critical step in the preparation of a build that is not to be neglected;
• Parametric studies carried out on two types of aluminum alloys—AlSi7Mg0,6 and AM205—have shown that the chemical composition of the aluminum alloy used has a significant influence on the set of operating parameters required to manufacture an acceptable aluminum alloy part. The energy density, ψ, which is the ratio of the laser power to the product of the lasing speed, the hatching distance, and the layer thickness, is conventionally used for the optimization of the operating conditions in SLM. Our experimental studies performed at different scales (1D and 3D) have shown the limits of this criterion. The combination of these results with the numerical simulation of the lasing of a single powder bead served as a basis for the definition of an initial model, the final objective of which will be to optimize the choice of manufacturing parameters.

Event localization