The stress corrosion cracking (SCC) susceptibility of 2195-T8 Al-Li alloy in N₂O₄ medium was evaluated using slow strain rate testing (SSRT). The electrochemical corrosion behavior and morphological evolution of the alloy under different conditions were further examined through potentiodynamic polarization measurements. The results indicate that with the increase in electrochemical corrosion rate, the corrosion morphology of the alloy extends from localized pitting and intergranular corrosion to severe exfoliation corrosion. In the N₂O₄ medium, the alloy exhibits significant susceptibility to SCC at tensile rates of ε ≥ 5 × 10⁻⁶ s⁻¹. However, when strained at ε = 10⁻⁶ s⁻¹, a sudden increase in I_SCC is observed accompanied by a transition to brittle intergranular fracture mediated by anodic dissolution. At the same stretch rate (ε = 10⁻⁶ s⁻¹), the susceptibility to SCC of the alloy in N₂O₄ medium increased with higher water content ω(H₂O). This trend is attributed to enhanced generation of HNO₃ and HNO₂, as well as increased diffusion of hydrogen—produced by the cathodic reaction—to the crack tip. The synergistic interaction between anodic dissolution and hydrogen embrittlement ultimately promotes the initiation and propagation of SCC in the alloy.

This work investigated the fatigue crack propagation behavior of the 2195-T8 Al-Li alloy with precorroded holes. The microstructure, crack growth path, and the fracture surfaces of the samples with the precorroded holes have been examined with scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), and computed tomography (CT). The characteristics of the crack growth have been analyzed via fracture mechanics by employing the finite element method (FEM). The results showed that the bulk of the fatigue cracks had been initiated from the corrosion pits and corroded discontinuously and precipitated further to become intergranular. Owing to the superposed stress concentration caused by the corrosion pits, the porous region at the bottom of the precorroded hole had affected the crack propagation performance. Crack growth rates were different in multiple positions owing to the difference of at crack fronts.

This study investigates the effects of heat transfer and molten pool flow behavior on the final structure of laser filler wire welds, aiming to improve weld quality. Laser filler wire welding experiments and numerical simulations were performed on 2195 Al-Li alloy workpieces with varying welding parameters. Numerical simulation of the heat transfer and flow in the molten pool was carried out using the CFD method, and the moving filler wire was introduced from the computational boundary by secondary development. Simulation results indicated that reducing welding speed and increasing wire feeding rate enhanced the cooling rate of the weld. Additionally, energy absorbed by the filler wire contributed between 6% and 16% of the total energy input during the liquid bridge transition. Comparing experimental and simulation data revealed that the cooling rate significantly affected the weld’s micro-structure and hardness. Notably, the formation of the equiaxed grain zone (EQZ) was crucial for weld performance. Excessive cooling rates hindered EQZ formation, reducing flow in this critical region. These findings offer valuable insights for optimizing welding parameters to enhance weld quality and performance.

In order to investigate the vibration characteristics of the object in the nondestructive test using thermosonics, the device for measuring vibration micro-displacement was built based on the laser displacement sensor and the ultrasonic excitation equipment. On this basis, the vibration displacement of the object was measured under the condition of ultrasonic loading with the frequency of 40 kHz and non-ultrasonic loading respectively. Then, the analysis on the frequency spectrum of vibration displacement obtained by the test was carried out. The obtained results show that there is fundamental frequency in the vibration spectrum of the object as well as the high-order harmonic frequencies, which confirms the existence of acoustic chaos in the thermosonics detection test. This work is of importance as it lays the foundation for the further investigation on the detection mechanism of thermosonics.