Recent advances in modeling fatigue cracks at microscale in the presence of high density coherent twin interfaces

This concise review chronicles recently emerged fatigue crack growth behaviors of nanomaterials with prevalent R3 boundaries and the related modeling endeavors. Experimentally, these nano-twinned materials demonstrated remarkably high damage tolerance, which is a significant countertrend to the previous nanocrystalline literature. To explore the physical rationale, various slip transfer mechanisms at a coherent twin-matrix interface are investigated using crystal simulations. The role of different slip-interface reactions is identified as modifying the cyclic slip irreversibilities, which in turn drives the crack advancement. As the residual Burgers vector from a reaction attains maxima, the associated fault energetics is predicted to saturate, which is an important discovery regarding the damage mechanism. Consequently, a generic computational recipe for theorizing material degradation is established, using reaction-specific Peierls stresses as crucial input. A general agreement between predictions and experiments lends sufficient credence to the adopted modeling approach. We also survey relevant literature and point out promising avenues for future research.