Molecular dynamics simulations of quasi-brittle crack development in iron

The paper presents the results of molecular dynamics (MD) simulations of three-dimensional kinetics of micro-crack propagation in alpha-iron and the accompanying lattice transformations at the crack tips. We show that crack initiation on {0 0 1} planes in iron is preceded with the emission of compact slip bands from the pre-crack tips, in agreement with the predictions of the earlier quasi-two-dimensional simulations. The application of Voronoi decomposition technique for atomic short-range order processing has allowed us to clarify the kinetics of structural transformations at the tips of nucleating and propagating cracks for three most common systems of crack propagation in iron. It is demonstrated that the compact slip bands emanating from the crack tips not only accompany crack nucleation, but remain an essential feature of the crack propagation on {0 0 1} planes. Due to the strong coupling between the crack tip and slip band propagation, the crack propagation can be limited by slip band interaction with microstructural obstacles, abundantly created in ferritic–martensitic steels in radiation environment of nuclear facilities.