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Abstract

The fracture behavior of lamellar Ti-Al alloys is strongly influenced by the twin interfaces in the microstructure. Molecular dynamics (MD) simulations are a valuable tool to systematically study crack-interface interactions with atomistic resolution, but their results are often crit- icized as being too academic. Experimental validation is difficult, because controlling the initial notch orientation is very challenging and the crack tip is never as sharp as in the typical MD set-ups. We in- vestigate this issue by studying crack-tip interface interactions at various coherent and semi-coherent interface types in nano-lamellar Ti-Al,using different crack configurations to differentiate the effects of the microstructure from those of the crack geometry. Results show that the semi-coherent pseudo twin (PT) interface is the strongest barrier for crack propagation while the coherent true twin (TT) interface is the weakest. The initial crack orientation has a bigger influence on this effect than the aspect ratio of the microcrack. The stress shielding behavior of the interfaces is also found to be strongly dependent on the initial crack configuration, however, the coherent TT interface remains the most effective interface in terms of shielding in all cases.