Effect of martensite twins on local scale cleavage crack propagation in a medium carbon armor grade steel

This paper proposes the efficacy of martensite nano-twins in a medium carbon armor grade martensitic steel on the cleavage crack resistance at a local scale. Concurrent analyses through electron channeling contrast imaging and electron back scattered diffraction techniques reveal that fine twins of width less than 10 nm are ineffective in deflecting the crack, propagating in the {100} cleavage plane. Coarse twins, on the other hand, resist the crack propagation by deflecting the crack through stepwise crack path propagations, e.g., a combination of matrix-twin {100} cleavage cracking or a combination of matrix {100} and twin-matrix {112} interface cracking. The interfacial cracking along the {112} twin boundaries is attributed to the presence of carbon enriched clusters along the twin boundaries.