Influence of tool head geometry on in situ monitoring of temperature, force, and torque during additive friction deposition of aluminum alloy 2219

Additive friction stir deposition (AFSD) has emerged as an effective method for producing uniform grain structures with enhanced mechanical properties. However, in the field of AFSD, there remains a lack of a systematic and clear description regarding the specific impact of tool head geometry on the structure and properties of fabricated deposits. This study investigates the effect of tool head geometry on aluminum alloy 2219 (AA2219) fabricated by AFSD. In situ monitoring data showed that deposition using a tool with two protrusions promoted sufficient material flow and increased plastic deformation. This resulted in a refined microstructure without abnormal grain growth. Enhanced mechanical properties were observed, including a microhardness of 92.2 HV0.5, yield strength of 315.8 MPa, ultimate tensile strength of 371.6 MPa, and an elongation of 6.8%, which were attributed to grain refinement and precipitation strengthening. Furthermore, corrosion resistance improved compared to deposits fabricated without protrusions, owing to grain refinement and a reduction of the aluminum–copper phase. The findings advance the understanding of the solid-state additive manufacturing process and offer new insights into achieving high-quality AA2219 deposits.