Solid-State Additive Manufacturing of AA6060 Employing Friction Screw Extrusion Additive Manufacturing

Solid-state additive manufacturing constitutes a worthwhile alternative for many precipitation-based aluminium alloys that cannot be processed through fusion-based approaches due to metallurgical problems. In this work, the newly developed solid-state friction screw extrusion additive manufacturing (FSEAM) approach has been employed to study the processability of AA6060 T6 as a function of the printing velocity. Various wall-like builds were fabricated at printing velocities of 100 mm/min to 250 mm/min by deposition of 50 layers of 1 mm thickness, 14 mm width, and 150 mm length. No major defects were observed in cross section, and the microstructure showed equiaxed grains with an average size of 2-4 & mu;m for all builds. Promising mechanical properties were obtained for all tensile test specimens extracted in the deposition direction of the layers. For specimens extracted in the build direction, only the builds fabricated with sufficiently high normal force to ensure proper bonding between successively deposited layers showed similar results to the deposition direction. The relatively high temperatures obtained during fabrication led to the dissolution of strengthening precipitates for the 150-250 mm/min samples as indicated by serrated yielding effects. Post-manufacturing heat treatment of these samples was successful, partially restoring the feedstock hardness.