Screw-fed powder-based additive friction stir deposition: A study on pure aluminum

Solid-state additive friction stir deposition (AFSD) is an innovate manufacturing process that offers significant advantages for near-net-shape manufacturing of aluminum alloy components. Different from the rod-based and wire-based AFSD, the powder-based AFSD can realize continuous solid-state deposition of metal materials. It is also applicable to a wider range of material systems and can achieve free alloy design through powder mixing. Compared with powder bed-based AFSD, the deposition efficiency of the screw-fed powder-based AFSD (SFP-AFSD) is increased by more than 4 times (150 cm³/h), greatly improving the powder utilization rate. In this work, pure aluminum powder was fed into a stirring tool with a rotating screw to soften the metal powder and successfully deposit it on a substrate. The investigation focuses on heat accumulation during the stirring tool lifting and steady-state deposition stages, revealing the impact of thermomechanical history on microstructure and mechanical properties. Results indicate that the heat accumulation region has a more complex grain distribution, resulting in lower tensile strength (147 MPa) and elongation (53 %) compared to the steady-state region (159 MPa and 68 %). Industrial computed tomography (CT) shows excellent density in both central (0.25 % porosity) and edge positions (0.61 % porosity). In addition, we also conducted deposition experiments on 2319 aluminum alloy powder and preliminarily prepared additive components of different shapes. This work provides insights into continuous solid-state additive manufacturing of metals.