Intergranular fracture, grain-boundary structure, and dislocation-density interactions in FCC bicrystals

Area of Science:

• Materials Science
• Mechanical Engineering
• Computational Modeling

Background:

• Understanding material failure is critical for engineering applications.
• Grain boundary (GB) structure and orientation significantly influence mechanical properties.
• Dislocation interactions at GBs are key to fracture nucleation and propagation.

Purpose of the Study:

• To predict and understand fracture nucleation and propagation mechanisms at different grain boundary types.
• To investigate the role of dislocation pileups, GB structure, and orientation in material failure.
• To compare fracture behavior between low-angle grain boundaries (LAGBs) and high-angle grain boundaries (HAGBs).

Main Methods:

• Dislocation-density based crystalline plasticity (DCP) modeling.
• Nonlinear finite element (FE) analysis.
• Micropillar experiments to obtain accurate GB orientations and structures.

Main Results:

• Higher normal stress, pileup density, and dislocation accumulation were observed at LAGBs compared to HAGBs.
• Fracture initiated and propagated at lower nominal strains for HAGBs than for LAGBs.
• DCP and FE analyses successfully predicted and explained fracture behavior based on microstructural mechanisms.

Conclusions:

• Fracture initiates at lower strains in HAGBs due to distinct dislocation interactions and pileups.
• GB structure and orientation are critical factors controlling fracture nucleation and propagation.
• The study provides fundamental insights into material failure mechanisms at grain boundaries.