Molecular dynamics simulation of the interaction of a nano-scale crack with grain boundaries in α-Fe

• Published in: Computational materials science 2017-09, Vol.137, p.85-99
• Main Authors: Kedharnath, A., Panwar, Ajay Singh, Kapoor, Rajeev
• Format: Article
• Language: English
• Subjects: Grain boundary crack interaction; Molecular dynamics simulation; Symmetric tilt grain boundary
• ISSN: 0927-0256; 1879-0801
• DOI: 10.1016/j.commatsci.2017.05.026

[Display omitted] The interaction of nano-scale cracks with grain boundaries in α-Fe were studied using symmetric tilt grain boundaries with [112¯] and [1¯10] tilt axis. For each tilt axis four types of grain boundaries were chosen – low angle, general high angle, Σ3 and Σ11. A crack perpendicular to the boundary plane was introduced between the two boundaries. The grain boundaries were equilibrated using molecular statics simulation and the entire configuration was deformed at constant strain rate using isobaric-isothermal (NPT) ensemble at 0K. The stress strain behaviour of the configurations, variation of dislocation line density with strain and the screening effect of the grain boundaries were studied. The strain field around the crack tip and the dislocations emitted from it interact with the grain boundaries. The configuration with Σ3 grain boundaries showed higher tensile strength while that with Σ11 showed lower tensile strength. This was attributed to the orientation of the dislocations in the {11¯0} boundary plane with 180° tilt angle and the complete coherency with {1¯1¯2} boundary plane with 70.53° tilt angle. Further, in both the Σ3 grain boundary configurations, even the most favourable slip system had a low Schmid factor, thus making slip difficult in the grain too. The configurations with 4.9° and 31.59° tilt angle about the [1¯10] tilt axis showed the most effective stress screening.