Temperature and strain-rate dependence of surface dislocation nucleation.
Ting Zhu1, Ju Li, Amit Samanta
1Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332, USA. ting.zhu@me.gatech.edu
Physical Review Letters
|February 1, 2008
Summary
Surface dislocation nucleation initiates plastic deformation in small solids. This study models this process, revealing a small activation volume influencing material strength and size-dependent behavior in experiments.
Area of Science:
- Materials Science
- Solid Mechanics
- Nanotechnology
Background:
- Plastic deformation in crystalline solids is governed by dislocation nucleation.
- Free surfaces can act as critical sources for dislocations, influencing material behavior.
- Understanding surface effects is crucial for small-volume materials.
Purpose of the Study:
- To develop an atomistic modeling framework for surface dislocation nucleation.
- To investigate the probabilistic nature of dislocation nucleation at surfaces.
- To determine the relationship between surface nucleation and material strength.
Main Methods:
- Atomistic modeling framework development.
- Simulation of dislocation nucleation at free surfaces.
- Analysis of activation volume and its dependence on temperature and strain rate.
Main Results:
- Characterized activation volume for surface dislocation nucleation (1-10b³).
- Demonstrated sensitive temperature and strain-rate dependence of nucleation stress.
- Established an upper bound for the size-strength relation in nanopillar experiments.
Conclusions:
- Surface dislocation nucleation is a key factor in small-volume plasticity.
- The probabilistic nature and small activation volume of surface nucleation significantly impact material strength.
- Findings provide critical insights for designing and interpreting experiments on nanostructured materials.
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