2D Ultrasonic-Assisted Burnishing to Control Surface Integrity and Electrochemical Behavior of AA7075-T6 Aluminum Alloys

Surface damage and corrosion are two major challenges in the long-time functional service life of industrial components. The surface modification approach was previously utilized to improve surface properties and increase corrosion resistance. This paper presents a comprehensive experimental investigation of ultrasonic-assisted burnishing to control surface integrity and corrosion performance of aerospace AA7075-T6 aluminum alloys. To this end, turned sample (control) was treated by conventional burnishing (without ultrasonic vibration), followed by 2D ultrasonic-assisted burnishing. The effect of radial and feed directional vibration on burnishing performance was evaluated. The surface roughness, microstructure, microhardness, and corrosion resistance of the treated samples were assessed. Results indicated that the mean surface roughness of the control sample (turned) was 0.247 µm which decreased to 0.121, 0.081, 0.023, and 0.067 µm after conventional burnishing (CB), ultrasonic-assisted burnishing on radial direction (R-UAB), ultrasonic-assisted burnishing on feed direction (F-UAB), and two-dimensional ultrasonic-assisted burnishing (2D-UAB), respectively. Grain refinement occurred after all burnishing processes and microhardness increased in the depth of 40 µm from 109 HV to 140, 186, 147, and 181 HV after CB, R-UAB, F-UAB, and 2D-UAB treatment, corresponding to 28, 70, 34, and 66% increase, respectively. In addition, the corrosion rate of control sample (turned) was 0.0858 mm/y which was decremented to 0.0541, 0.0498, 0.0249, and 0.0386 after CB, R-UAB, F-UAB, and 2D-UAB treatments, respectively. Interestingly, ultrasonic-assisted burnishing, in particular, along the feed direction outperformed the other treatments by reducing surface roughness and the corrosion rate by about 90 and 71%, respectively. Graphical Abstract