5. AlSi10Mg Nanocomposites Prepared by DMLS Using In-Situ CVD Growth of CNTs: Process Effects and Mechanical Characterization

Carbon Nanotube (CNT) reinforced AlSi10Mg Metal Matrix Composites (MMCs) were fabricated through direct metal laser sintering (DMLS), and select mechanical properties were compared to those of virgin DMLS AlSi10Mg. The MMCs were prepared by initially depositing CNTs homogeneously on the bulk AlSi10Mg powder through the chemical vapor deposition (CVD) process. The CNT-reinforced AlSi10Mg (CNT-Al MMC) powder was then fused together through DMLS using an EOS M290 additive manufacturing printer. Virgin AlSi10Mg powder was processed as a separate build via DMLS for baseline comparison. Scanning Electron Microscopy was conducted and material property characterization was performed to observe surface morphology, microstructure and mechanical property variation of these materials. Further analysis via Scanning Electron Microscopy and Energy-Dispersive X-ray spectroscopy revealed homogeneously distributed voids within the microstructure of the CNT-Al MMC and large quantities of oxygen near these voids. The growth of CNTs directly onto powder particulates, via CVD, allows for the uniform distribution of reinforcement, which is critical to cohesive 3D printed builds. However, this process requires refinement to limit the presence of excess oxygen, which can cause microstructural defects, thereby hindering the reinforcing capabilities of CNTs.