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

A Kedharnath and AS Panwar and R Kapoor, COMPUTATIONAL MATERIALS SCIENCE, 137, 85-99 (2017).

DOI: 10.1016/j.commatsci.2017.05.026

The interaction of nano-scale cracks with grain boundaries in alpha-Fe were studied using symmetric tilt grain boundaries with 11 (2) over bar and (1) over bar 10 tilt axis. For each tilt axis four types of grain boundaries were chosen-low angle, general high angle, E3 and Ell. 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 0 K. 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 E3 grain boundaries showed higher tensile strength while that with Ell showed lower tensile strength. This was attributed to the orientation of the dislocations in the 1 (1) over bar0 boundary plane with 180 degrees tilt angle and the complete coherency with (1) over bar(1) over bar2 boundary plane with 70.53 degrees tilt angle. Further, in both the E3 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 degrees and 31.59 degrees tilt angle about the 110 tilt axis showed the most effective stress screening. (C) 2017 Elsevier B.V. All rights reserved.

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