The Corrosion Properties of Al-Cu-Mg Alloy Fabricated via Additive Friction Stir Deposition

Using as-received Al-Cu-Mg bars as the raw material, a 530 mm diameter Al-Cu-Mg alloy ring component was successfully fabricated via additive friction stir deposition (AFSD). Owing to the severe plastic deformation and dynamic recrystallization induced during the AFSD process, the microstructure was noticeably refined. The average grain size decreased from 35.84 μm to approximately 3.40 μm, with over 90% of grains below 4 μm. Electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization tests in 3.5 wt.% NaCl solution revealed that the AFSD-ed alloy exhibited a higher corrosion potential of −675.29 ± 7.78 mV (vs. Saturated Calomel Electrode, SCE) and a lower corrosion current density of 1.45 ± 0.04 × 10−6 A/cm2, compared with −684.33 ± 0.86 mV and 4.33 ± 1.30 × 10−6 A/cm2 for the as-received bar, respectively. EIS further confirmed superior corrosion resistance, as evidenced by larger capacitive arcs and a higher low-frequency impedance modulus. Microstructural characterization indicated that the corrosion mode, from propagating pits to isolated pits, is probably due to the refined grains and secondary phase particles during AFSD. These findings demonstrate that AFSD enables large, fully dense Al-Cu-Mg components with enhanced corrosion resistance, establishing AFSD as a promising route to improved corrosion performance for aerospace and defense applications.