Plastic deformation by conservative shear-coupled migration of tilt boundaries with intergranular nano-cracks or precipitates

Abstract

We present molecular dynamics (MD) simulations of the shear-coupled migration (SCM) behaviour of symmetrical tilt boundaries perturbed by the presence of nano-cracks or nano-precipitates lying on the boundary plane. The simulations have been performed for copper bicrystals at room temperature (300 K). The tilt boundary gets pinned by the crack tip or precipitates; shear-coupled migration occurs only ahead of the pinning points. Bulging of the tilt boundary reduces the shear stress on the boundary surface near the pinning points. In the case of cracks, the local deviation of the boundary from the crack plane close to the crack tip hinders mode II crack propagation; in fact, crack healing is observed in some cases. The applied stress grows until depinning of the boundary takes place by SCM bulging or by the combined action of SCM with another deformation mechanism (emission of dislocations from the pinning point vicinity, grain boundary sliding).

Keywords:

• grain boundaries
• shear-coupled migration
• stress driven migration
• tilt grain boundaries
• molecular dynamics
• intergranular nano-cracks

Acknowledgements

This work was supported by the Department of Industry, Commerce and Tourism of the Basque Government (project ETORTEK inanoGUNE). A. Luque also acknowledges the Spanish Ministry of Science and Innovation and the European Social Fund (Torres Quevedo Programme).