Effect of corrosive environment and stress ratio on the fatigue crack growth behavior of titanium alloy

This study investigated the fatigue crack growth behavior of Ti−6Al−4V ELI titanium alloy, focusing on different stress ratios and environments (air and saline). The results showed that corrosive environment and high stress ratio increased the rate of fatigue crack growth, especially in the steady stage of crack propagation. Fatigue crack growth rates in the linear extension stage were fitted by the Paris model, and high accuracy was obtained. The crack paths were analyzed through electron backscatter diffraction (EBSD) and scanning electron microscope (SEM) analysis, revealing a zigzag pattern and transgranular fracture. The cracks deflected and changed direction as they intersected the slip system with different Schmidt factors and crossed low angle grain boundaries. It was found that the basal sliding system or prismatic sliding system was more active in the saline environment, while pyramidal slip systems were primarily distributed in air. The fatigue crack growth rate model and microscopic observations provided insight into the macroscopic crack extension behavior under corrosive environments, allowing researchers to understand the mechanisms driving crack propagation and the effects of environmental factors on the process.