Corrosion Resistance and Fatigue Life of Al 7075 Parts Prepared by High-Rate Additive Fiction Stir Deposition

Abstract This study investigates the electrochemical corrosion resistance and fatigue life of as-fabricated Al 7075 parts made with high-rate additive friction stir deposition (AFSD). The relationship between microstructural changes and corrosion behavior was examined, along with assessments of bending fatigue life and damping capacity. Al 7075-T6 feedstock rods were deposited with a high feed rate (254 mm/min) and a high tool traverse velocity (276.9 mm/min). Tafel polarization test results revealed increases in corrosion current density from 1.9 × 10 −4 A/cm 2 for the feedstock to 3.3 × 10 −4 and 3.8 × 10 −4 A/cm 2 for the deposition top and bottom layers, respectively. Additionally, the corrosion potential decreased after processing, with a more pronounced reduction observed in the bottom layers, from − 0.95 to − 0.99 V. Electrochemical impedance spectroscopy results showed that the high-frequency capacitive arc decreased after AFSD, indicating reduced corrosion resistance, especially in the bottom layers. Moreover, a decline in fatigue life was observed, decreasing from 221,000 cycles to 174,000 and 164,000 cycles for the top and bottom deposition layers, respectively. The reduction in fatigue life from the top to the bottom layers was accompanied by an increase in damping values in the as-fabricated parts. These changes were attributed to the microstructure alterations during the AFSD, particularly the nonuniform distribution and coarsening of MgZn-rich precipitates. Coarsening was more pronounced in the bottom layers due to prolonged heat exposure during processing.