Ductile-brittle behavior of (001)[110] nano-cracks in bcc iron

摘要

We carry out atomistic simulations and stress analysis of crack behavior in bcc iron under Mode I, quasi-static loading. We observe that the formation of unstable stacking faults at the crack tip of a relatively long crack (～16nm) cannot prevent unstable crack extension at the Griffith level. A crack of smaller dimensions (～4 nm) produces twinning on the < 111 > {112} slip sysem ahead of the tip, which gives rise to a slow ductile growth during subsequent quasi-static loading. The influence of the T-stress on the shear processes at the crack tip and crack stability is discussed.