Assessing the intergranular crack initiation probability of a grain boundary distribution by an experimental misalignment study of adjacent slip systems

Crack initiation at grain boundaries due to blocked slip transfer of dislocations is a main failure mechanism during the fatigue of metals. A quantification of the resistance effect of a grain boundary is needed to assess a textured or texture-free microstructure for fatigue strength. Geometric approaches based on the misalignment of slip systems in adjacent grains are widely used. Hence, we validated the geometric transmission factor of Shen et al. in coarse-grained high-purity aluminum under the assumption that the combination of a large slip activity and a blocked slip at a grain boundary leads to intergranular crack initiation and revealed that a detailed knowledge of the 3D-orientation of the grain boundary is essential. Thereby we gathered information about the 3D-microstructure using FIB-cross-sectioning. Hence it is possible to evaluate potential crack initiation sites for a specific microstructure or to estimate the fatigue strength of a textured microstructure in terms of a crack initiation probability.