Al-Matrix Nanocomposites via Laser Powder Bed Fusion Process: Production and Characterization

Additive Manufacturing (AM) has emerged as a method for producing metal components that combine intricate geometries with tailored engineered microstructures. Among the AM approaches, Laser Powder Bed Fusion (LPBF) has been proven effective for fabricating high-density Aluminum (Al) alloys. Yet, it faces challenges due to Al's high reflectivity, its tendency to oxidize, and the thermal stresses that can complicate the processability of Al-based alloys. To overcome these challenges, the incorporation of nanoscale reinforcements has recently attracted interest. This thesis examines the manufacturing and characterization of AlSi10Mg reinforced with Graphene Nanoplatelets (GNPs) via LPBF, explicitly focusing on the mechanical properties and microstructural quality of AlSi10Mg compared to AlSi10Mg-GNPs nanocomposites. Gas atomized AlSi10Mg powders were blended via ball milling with 0.1 wt.% and 0.3 wt.% of GNPs. Then, they were processed on a TRUMPF TruPrint 1000 system at two distinct Volumetric Energy Densities (VEDs) equal to 50 and 71 J mm⁻³. The study provides an assessment of densification behavior, surface morphology, microstructural features, and mechanical performance using Archimedes’ density measurements, X-ray Computed Tomography (XCT), Optical Microscopy (OM), Scanning Electron Microscopy (SEM), nanoindentation, and uniaxial tensile testing. The experiments showed that all compositions had densification exceeding 97%, while the benchmark AlSi10Mg alloy still had the highest density, around 98.8%. Yet, increasing GNPs to 0.3 wt.% had the opposite effect, as the melt pool became steadier, porosity decreased, and densification increased compared to 0.1 wt.%. The tensile tests indicated a trade-off between strength and ductility. At the same time, the unreinforced alloy achieved a tensile strength of 816 MPa and elongated to about 5.7 % before fracture, whereas the 0.1 wt.% and 0.3 wt.% alloys.% GNPs-reinforced specimens had only a moderate strength range of 640-676 MPa. However, they still displayed ductility on par with the base material as the VED increased. Complementary nanoindentation experiments showed that additions of 0.1 wt% and 0.3 wt% resulted in a drop in hardness due to GNP clustering, although there was a local stiffness enhancement at 0.1 wt% % GNPs. Overall, the data show that GNP-reinforced AlSi10Mg, when paired with tuned LPBF settings, alters melt pool dynamics and microstructure, enabling the production of Al matrix nanocomposites that are both highly dense and almost defect-free. These results demonstrated noteworthy insights into the final properties of LPBF-fabricated AlSi10Mg-GNP nanocomposites and help pave the way for the development of next-generation lightweight nanocomposites for automotive and aerospace applications.