The Influence of the Deposition Speed during Friction Screw Extrusion Additive Manufacturing of AA6060

Abstract

Solid-state additive manufacturing may solve critical issues typically arising during fusion-based additive manufacturing of high-strength aluminium alloys. In this work, the recently introduced Friction Screw Extrusion Additive Manufacturing (FSEAM) process was employed to manufacture wall-like rectangular builds of AA6060 T6 deposited with deposition speeds from 300 mm/min to 500 mm/min. All builds were manufactured at a tool rotation rate of 400 rpm with 1 mm layer thickness. The volumetric supply rates were adjusted to maintain constant build width. Solid builds were formed without major defects over the full range of deposition speeds. The process generated sufficient normal force and heat at all deposition speeds which resulted in manufacturing of defect free builds. The resulting average grain size was consistently below 5 micrometer throughout all builds independent of deposition speed or location through the height. Microhardness measurements revealed a decrease in hardness from a feedstock value of 80 HV to around 50 HV in all manufactured builds. Tensile tests in the building direction showed consistent results for all the samples as a result of defect-free parts, demonstrating a tensile strength of approximately 150 MPa, yield strength of 100 MPa, and uniform elongation of 12-15%. The fracture surfaces revealed large amounts of dimples at all deposition speeds in line with the high degree of plastic deformation preceding fracture observed from the tensile tests. The obtained results indicated that FSEAM is a promising process for solid-state additive manufacturing of aluminium alloys.