Effects of 3D microstructural distribution on short crack growth behavior in two bimodal Ti-6Al-4V alloys

In situ X-ray micro-tomography was performed to analyze the short crack growth in the 3D microstructure of two bimodal Ti-6Al-4V alloys with predominant alpha + beta and alpha phase volume fractions. Short crack strongly interacts with the local microstructure and it grows into the predominant phase above the average microstructural fraction in each alloy. The higher volume fraction and size of the alpha grains in the microstructure induce crack growth with lower variations and larger deflection lengths inside the alpha grains. As the short crack length increases, the larger deflections left behind the crack front induces higher crack closure that decreases the crack driving forces. As a result, the short crack remains sensitive to the local microstructural features at higher lengths.