Enhancing dislocation emission in nanocrystalline materials through shear-coupled migration of grain boundaries

Abstract

a b s t r a c tA theoretical model has been developed to illustrate the effect of shear-coupled migration of grain boundaries on dislocation emission in nanocrystalline materials. The energy characteristics and critical shear stress τ c that is required to initiate the emission process were determined. The results obtained show that the dislocation emission can be considerably enhanced as shear-coupled migration was the dominating process; a critical coupling factor that corresponded to the minimum τ c , which led to an optimal dislocation emission, was also discovered. The proposed model has also been quantitatively validated by the existing molecular dynamics simulations.

A coupling crack blunting mechanism in nanocrystalline materials by nano-grain rotation and shear-coupled migration of grain boundaries

“…Investigations of the present authors have shown that the SCM mode can considerably enhance the intrinsic ductility [6], toughness [15], crack blunting [16] and dislocation emission [17] in NC materials. The coupled NGR-SCM process proposed by Li et al [11] has also been identified as an effective toughening mechanism in NC materials [14].…”

Strong crack blunting by shear-coupled migration of grain boundaries in nanocrystalline materials

“…The SCM mode has been identified as a general toughening mechanism [20,21], and can considerably enhance the intrinsic ductility of NC materials [22,23]. Moreover, our recent study has shown that SCM was in favor of the dislocation emission from the disclinated grain boundaries [24]. Therefore, one may deduce that SCM could also influence the dislocation emission from a crack tip, thus leading to crack blunting and abundant activation of dislocations in the grain interior, and eventually giving rise to the enhanced ductile feature, which appeared in some NC materials as observed in experiments [3,5,7,8,25].…”

Atomistic simulation of mechanical behaviours of nanocrystalline AI alloys with grain boundary segregation

“…2.6) [85][86][87][88]. Simultaneous GBS and GBM, also called the shear-coupled migration of GBs, result in a grain rotation which changes the GB misorientation angle and can be responsible for the enhancement of dislocation emission in the NC structure [89]. GBS and the shear-coupled migration reduce the energy required for deformation and increase the plasticity of polycrystalline materials [90,91].…”