A Feasibility Study on Friction Screw Extrusion Additive Manufacturing of AA6060

Abstract

Additive manufacturing in the solid state opens up possibilities for many alloys that are not suitable for fusion-based approaches. Following the advances in friction-based joining processes for high-strength aluminum and magnesium alloys, the Friction Screw Extrusion Additive Manufacturing (FSEAM) process has been developed for deposition of thin layers for cladding and additive manufacturing on a variety of substrates. In this work, the first results on the manufacturing of wall-like rectangular builds from AA6060T6 are reported. Multiple layers of about 15 mm width and 1 mm thickness were deposited with print velocities of 100–250 mm/min at constant tool rotation speed. Solid walls were formed without major macroscopic defects. Promising mechanical properties were measured with a yield strength of about 80 MPa and a tensile strength increasing from 112 to 144 MPa as function of the print velocity. The material was characterized by a fine microstructure with an average grain size below 10 μm for all builds. At the microscale, strings of unbonded regions have been observed at lower print velocities possibly related to insufficient mixing of the deposited material with the previous layer during manufacturing leading to reduced ductility. The observed results are encouraging, indicating that additive manufacturing of aluminum alloys through FSEAM is feasible after further optimization of the process.KeywordsAdditive manufacturingAA6060T6Screw extrusion