Grain boundary plasticity initiated by excess volume

Area of Science:

• Materials Science
• Solid Mechanics
• Crystallography

Background:

• Grain boundaries (GBs) are crucial in crystalline solids, acting as barriers to dislocation motion and facilitating plastic deformation.
• The excess volume at GBs provides a microscopic degree of freedom for plasticity, a phenomenon not fully explained by classic geometric models.
• Identifying the atomistic mechanisms of GB plasticity has been challenging due to their transient nature.

Purpose of the Study:

• To unveil a general and inherent route for initiating grain boundary (GB) plasticity.
• To elucidate the role of excess volume and topological transitions in GB plasticity.
• To establish a stress-triaxiality-based criterion governing this microscopic degree of freedom.

Main Methods:

• Utilizing gold (Au) polycrystals as a model system.
• Employing advanced characterization techniques to observe atomistic processes during deformation (details not specified in abstract).
• Analyzing the correlation between excess volume, topological transitions, and plastic deformation at GBs.

Main Results:

• A general route for initiating GB plasticity via transient topological transitions was identified.
• The excess volume at GBs was confirmed as the trigger for these transitions.
• A stress-triaxiality-based criterion was established to govern the microscopic degree of freedom at GBs.

Conclusions:

• The study provides a new perspective on the mechanisms of plastic deformation at grain boundaries.
• Findings highlight the significance of microscopic degrees of freedom in GB plasticity.
• This research contributes to a more comprehensive understanding of GB behavior in crystalline materials under stress.