Transitional effect of 3D microstructural features on short crack growth behavior in Ti-6Al-4V alloy

Abstract

In this study, the complex 3D microstructure and short crack in a Ti-6Al-4V alloy were reconstructed by employing the X-ray micro-tomography coupled with EBSD serial sectioning. Global sensitivity analysis can be used to determine the most important features affecting the crack growth behavior. Afterwards, using a surrogate model, the relationship between microstructural features and short crack growth can be further analyzed. Using the aforementioned approach in a Ti-6Al-4V, it was found that a high number of α grains in contact with a long cracked α grain in the loading direction may impose a constraint on the crack opening resulting in low crack growth rate. As the crack length increases, crack bifurcations and formation of secondary cracks in surrounding grains leads to a decrease of crack driving forces at the crack front with lower average crack growth rates.