Microstructural, thermal, and physical characterisations of highly-filled PLA-Al6061 polymer-metal composite filament for metal additive manufacturing via material extrusion

This study introduces detailed characterisations of a novel highly-filled PLA-Al6061 polymer-metal composite filament (69.0 wt.% Al6061, remainder PLA) for metal additive manufacturing (AM) via material extrusion, specifically fused filament fabrication (FFF). The filament, synthesised through controlled blending, compounding, and extrusion processes, was evaluated for its microstructural, thermal, and physical properties. Scanning electron microscopy (SEM) revealed a homogeneous dispersion of Al6061 particles (average size 60 ± 10 μm) within the PLA matrix, with energy-dispersive X-ray spectroscopy (EDX) confirming Al dominance alongside C and O from the polymer. X-ray fluorescence (XRF) indicated 91.08% Al in the metal phase, consistent with Al6061 alloy composition, while X-ray diffraction (XRD) identified a face-centered cubic (FCC) Al phase. Thermal analysis via differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) showed PLA melting at 172.61°C (ΔH = 5.01 J/g) and decomposition at 310.53°C (23.60% weight loss), potentially supporting subsequent debinding and sintering processes for fully dense metallic parts later. Physical properties, including average surface roughness (R a = 10.36 ± 1.22 μm) and Vickers microhardness (60.4 HV) suggest green part robustness, which was successfully printed by using a typical desktop FFF 3D printer. These results demonstrate the potential of the filament for producing robust, cost-effective metal parts via MEX-based FFF technology, advancing metal AM applications.