On crystallographic crack transfer across interfaces in four types of aluminum bicrystal

Crack growth behavior across grain boundaries (GBS) in four types of aluminum bicrystal, including[121] tilt symmetric,[121] tilt pseudosymmetric, [012]-[111], and[121] 180° tilt bicrystals, was studied. Cracks generally decelerate at Gbs in these bicrystals under a constant cyclic load. It was also found that the variation in growth rate at a GB depends on the relative orientation of the two grains on opposite sides of the GB, the GB microstructure, and the applied stress. Two modes of crack transfer across GBs were identified: at a GB with a pair of nearly parallel slip systems, located respectively, on its two sides, the crack transfers smoothly by following the pair of slip bands; at other GBs the crack splits, branches into up to three secondary slip bands, and decelerates dramatically at a constant cyclic stress. Interface-resistance to fatigue crack transfer across a GB was rationalized according to dislocation movement across it.