<p>Additive Friction Stir Deposition (AFSD) is an emerging solid-state additive manufacturing technology that can deposit metals without melting and solidification. This characteristic makes AFSD a potential alternative to traditional fusion-based additive manufacturing technologies. Although deposition rate is closely related to the additive efficiency of AFSD, its effects on microstructural and mechanical properties remain unclear. This study investigates the effects of deposition rate on microstructure and mechanical properties by conducting experiments at deposition rates of 0.2, 0.3, 0.4, 0.5, 0.6, and 1. AFSD multi-layer structures were fabricated at different deposition rates, and specimens for microstructure and mechanical property testing were extracted using wire-cut EDM. The relationship between deposition rate, microstructure, and mechanical properties was analyzed through electron backscatter diffraction (EBSD), tensile testing, and hardness testing. At deposition rates of 0.2, 0.4, and 0.6, the average grain sizes were 9.5, 11.8, and 13.8&#xa0;μm, respectively, indicating a positive correlation between grain size and deposition rate. However, the ultimate tensile strength decreased with increasing deposition rate, reaching 215, 203, and 196&#xa0;MPa at deposition rates of 0.2, 0.4, and 0.6, respectively. Combining test results for heat input, friction torque, and axial force, the study demonstrates that variations in deposition rate induce changes in thermal and force inputs during the AFSD process, subsequently driving the evolution of microstructure and mechanical properties. Specifically, increased deposition rate leads to higher plastic deformation heat input and greater axial force, ultimately resulting in grain growth and diminished mechanical performance. The results provide an important reference for optimizing AFSD and increasing additive manufacturing efficiency.</p>