Triple junctions constitute a significant volume fraction of bulk nanocrystalline metals, in which disclinations are typical junction defects. In this study, a disclinated tricrystalline nickel nanowire with three [001] tilt grain boundaries intersecting at 120° angles is simulated at zero temperature using the embedded atom method. The results show that a triple junction disclination is unstable if its strength attains a critical value, giving rise to a crack. The critical strength demonstrates a significant size effect. The cracking occurs preferentially on the grain boundaries, suggesting that some grain boundaries are more resistant to cracking than others. This also results in complex crack branching, which under an external load may enable the material to sustain a larger deformation before failure. The reported findings may have important implications on the development of fracture-resistant nanocrystalline metals through the control of grain boundary structures.

• Received 18 April 2007

DOI:https://doi.org/10.1103/PhysRevB.76.134105