Dislocation cross-slip in nanocrystalline fcc metals

Area of Science:

• Materials Science
• Nanomaterials
• Computational Materials Science

Background:

• Dislocation motion is fundamental to plastic deformation in crystalline materials.
• Grain boundaries significantly influence mechanical properties in nanocrystalline metals.
• Understanding dislocation behavior at grain boundaries is crucial for designing advanced materials.

Purpose of the Study:

• To investigate the dislocation cross-slip mechanisms in nanocrystalline aluminum (Al).
• To determine the role of grain boundary structure in controlling dislocation propagation.
• To elucidate how dislocations avoid stress concentrations at grain boundaries.

Main Methods:

• Constant strain rate molecular dynamics simulations were employed.
• Simulations focused on nanocrystalline aluminum under tensile loading.
• Analysis centered on dislocation nucleation, propagation, and cross-slip events.

Main Results:

• A significant fraction of nucleated dislocations exhibited cross-slip via the Fleischer mechanism.
• Dislocation cross-slip was strongly influenced by the local grain boundary structure.
• Cross-slip enabled dislocations to circumvent stress concentrations, preventing pinning.

Conclusions:

• Grain boundary structure dictates the occurrence and location of dislocation cross-slip.
• The Fleischer mechanism is a key pathway for dislocations to overcome pinning sites.
• This mechanism contributes to the deformation behavior of nanocrystalline aluminum.