Molecular dynamics simulations were used to study crack propagation in a Nickel single crystal and a Nickel-Aluminum bimetal interface. The embedded atom method interatomic potential was used to investigate the behavior of (001) [100] crack system under mode I loading in the two systems. The propagation mechanisms and fracture behavior and properties of a propagating crack in Ni were compared with propagation, behavior and properties of a surface crack in Ni-Al that initiates and propagates from Ni towards the Ni-Al bimetal interface. Our results for Ni show an initial brittle crack propagation followed by a roughening of the crack surfaces at one-third of the Rayleigh wave speed and are in agreement with previous investigations. In Ni-Al the crack surfaces initially grow brittle. However, two regimes of crack propagation velocities were observed in this case with crack getting decelerated as it nears the interface. Further dynamic analysis of the crack propagation indicated a cease in the crack propagation in Ni due to a brittle to ductile transition. In Ni-Al bimetal interface system, as the crack approaches the interface, a process zone representing local disorder at the crack tip was observed to start growing and interacting with interfacial defects that eventually results in a blunting of the crack tip.

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