Tension/compression asymmetry of grain boundaries with non-planar structure

Molecular dynamics simulations were carried out to investigate the mechanical property and the deformation mechanisms of Cu bicrystal with non-planar structured grain boundaries(GBs) under uniaxial tension and compression. The simulation results showed that the non-planar GBs could change their equilibrium configurations under the applied stress, and the deformation mechanisms varied when altering the misorientation angle. The stacking fault energy curve was affected by the stress perpendicular to the slip plane and therefore has an influence on the dislocation nucleation mechanisms. Previous studies have revealed a ubiquitous tension/compression (T/C)strength asymmetry of many ultra-fine or nanocrystalline materials, and a higher compressive strength was usually reported. However, in the present study, the bicrystal samples with non-planar structured GBs show a higher tensile strength than the compressive one. The unusual T/C asymmetry property has an implication that the GBs with non-planar structure can play a significant role in affecting the mechanical properties of nanostructured materials.