Research on the fatigue crack propagation mechanism of 2050Al-Li alloy with different pre-deformation quantities

The 2050 Al-Li alloy is widely used in the aerospace industry due to low density and other advantages. However, during long-term service, fatigue failure is an inevitable problem. Therefore, this paper mainly studies the fatigue crack propagation characteristics of 2050 Al-Li alloy with different pre-deformation amounts (0%, 4%, 8%, 12%, 16%, 20%). The results showed that when the pre-deformation amount was 0%, the resistance of fatigue crack initiation was the strongest (6.34 MPa·m 1/2 ), and the fatigue crack propagation rate was the lowest. After adding pre-deformation treatment, the fatigue crack propagation threshold value (Δk th ) decreased, and the propagation rate increased. Microstructure studies indicated that pre-deformation could provide more favorable positions for the nucleation of T 1 phase, resulting in a reduction in T 1 phase size and an increase in density. The reduction in T 1 phase size allowed dislocations to cut through, reducing stress concentration and effectively reducing the crack propagation rate. The increase in T 1 phase density reduced the dislocation movement space, leading to an increase in damage accumulation and accelerating the crack propagation rate. In addition, the addition of pre-deformation amount caused grain boundary softening, facilitating crack propagation along the grain boundaries. The mathematical model calculation shows that among the factors influencing the propagation of fatigue cracks, in order of increasing influence degree, they are: the density of T 1 phase > the length of T 1 phase > the dislocation density. The experimental results provide a certain theoretical basis for the performance optimization of the 2050 Al-Li alloy in practical engineering applications.