Minghe Chen

The 2A97 Al‐Li alloy is widely utilized in aerospace because of its excellent mechanical properties. However, when the alloy is exposed to a moist climate, its service life is seriously affected by surface corrosion. To address the issue, a superhydrophobic surface with enhanced corrosion resistance was successfully developed on the 2A97‐T3 Al‐Li alloy by constructing HCl/FAS composite structures. The alloy was etched in a 5 mol/L HCl solution for 8 min, and then it was immersed in boiling water for 30 min. Finally, the alloy was soaked in a 0.1 mol/L perfluorodecyltriethoxysilane (FAS‐17) solution for 2 h. The low‐adhesion coating of a water contact angle was 152.7°, and the rolling angle was 5.64°. The corrosion resistance of the modified alloy was significantly improved compared to the original alloy. Specifically, the corrosion potential increased from −0.732 to −0.408 V, and the corrosion rate decreased dramatically from 3.322 × 10 ⁻⁸ to 3.917 × 10 ⁻⁹ A/cm ² . The surface activity of the 2A97 Al‐Li alloy was reduced by these modifications. An innovative and effective method was provided to improve the corrosion resistance of the Al‐Li alloy. It holds significant promise for extending the service life of Al‐Li alloys in moisture‐prone environments.

The 2A12‐T4 aluminum alloy is widely applied as important structural components in aerospace. It is served in an environment with high humidity and high concentration of halogen ions for the long term, which accelerates the corrosion rate of the oxide film. Therefore, the service life of the alloy is seriously affected. To solve the above issue, the superhydrophobic surface is prepared through the combination of hydrochloric acid etching and boiling water bath heating. When the hydrochloric acid etching time is 5 min, the boiling water bath time is 20 min, the contact angle of the surface reaches a maximum value of 152.43°, and the water droplets can slide down autonomously. Besides, the corrosion resistance of the alloy is significantly enhanced: the corrosion potential value of the superhydrophobic surface increases from −0.3798 V _SCE to −0.2328 V _SCE , meanwhile the density value of the corrosion current decreases from 3.661 × 10 ⁻⁸ to 2.6525×10 ⁻⁹ A/cm ² . The value of corrosion inhibition efficiency reaches 92.75%. The value of R _CT increases from 14797 to 64298 Ω·cm ² . An effective method is provided to improve the corrosion resistance of high‐strength aluminum alloys by fabricating a superhydrophobic surface.

The influence of the strain on the formability of 2A97‐T3 Al–Li alloy during electric pulse‐assisted forming was investigated in the research. Electrically assisted stress relaxation tests were conducted, and a corresponding stress relaxation model was developed and validated. The mechanism of the pulsed current influences stress relaxation in the alloy was revealed based on the analysis of stress relaxation curves and microstructure. Optimal processing performance for the 2A97‐T3 Al‐Li alloy was obtained at 450 A, 12 ms pulse width, 60% duty cycle, and 50 Hz frequency. A yield strength of 89 MPa and an elongation of 13.2% were obtained under the conditions. Furthermore, a residual stress of only 0.142 MPa was recorded after relaxation at ε = 0.0667. Under combined the strain and the Joule heating, the grains were refined by dynamic recovery and recrystallization. Grains first coarsened and then they were elongated, while the proportion of low‐angle grain boundaries increased concurrently. Concurrently, the texture strength increased markedly. Its maximum intensity rose from 2.225 to 4.755, which was attributed to the mechanism of continuous dynamic recrystallization. It was demonstrated that the stress was effectively reduced and the formability of the alloy was significantly improved by means of electric pulse‐assisted forming.

Diffusion bonding (DB) of aluminum alloys faces significant technical challenges, requiring thorough surface preparation and precise control of process parameters. To enhance the joint quality of 7B04 aluminum alloy sheets, pure aluminum (Al) and 7075 aluminum alloy powders were used as interlayers. In the DB experiments, nano-sized Al powder and micro-sized 7075 powders with different particle sizes served as interlayer materials. Compared to DB without an interlayer, using powder interlayers substantially reduced the bonding temperature while improving overall joint performance, with deformation kept below 6%. The lap shear strength (LSS) of the bonded 7B04 joints was significantly higher when 45 μm and 75 μm 7075 powders were used, compared to the 5 μm 7075 powder. The joint with a 50 nm Al powder interlayer achieved a maximum LSS of up to 220 MPa and exhibited considerably higher microhardness. Additionally, the mixed Al/7075 powder interlayer effectively decreased voids at the joint interface, contributing to increased LSS.

The high-strength aluminum alloy 7B04 used in aircraft structures poses challenges in welding. In this study, 7075 aluminum alloy powder is used as an interlayer to strengthen the vacuum diffusion bonding (DB) joint of 7B04 aluminum alloy. Surface treatments with plasma activation before DB can effectively increase the bonding rate and lap shear strength (LSS) of the joint. The effects of DB temperature, pressure, and holding time on the joint LSS were analyzed by developing a quadratic regression model based on the response surface method (RSM). The model’s determination coefficient reached 99.52%, with a relative error of about 5%, making it suitable for 7B04 aluminum alloy DB process parameters optimization and joint performance prediction. Two sets of process parameters (505 °C-5.7 h-4.5 MPa and 515 °C-7.5 h-4.4 MPa) were acquired using the satisfaction function optimization method. Experimental results confirmed that the error between measured and predicted LSS is approximately 5%, and a higher LSS of 174 MPa was achieved at 515 °C-7.5 h-4.4 MPa.