Quantification of Resistance of Grain Boundaries to Short-Fatigue Crack Growth in Three Dimensions in High-Strength Al Alloys

Based on the previous three-dimensional (3-D) crystallographic model for short-fatigue crack propagation through grain boundaries, the resistance of a grain boundary to the crack growth was quantified as a Weibull-type function of the twist component of crack plane deflection across the boundary. The effective driving force for the crack at a grain boundary was quantified as the applied driving force minus the resistance. This allowed the quantification of variation in growth rate at different grain boundaries along the crack front. The model could simulate satisfactorily that the crack front at the grain boundaries with high twist angle indeed was lagged behind those with low twist angle and that the crack growth rate on the surface varied significantly. The model was also used to predict short-fatigue crack growth statistically in different textures, showing potential application to texture design of alloys. Subsequent work still needs to be done to incorporate other factors, such as the tilt angle and Schmidt factor, into the model to render a more accurate simulation.