Intermittent dislocation density fluctuations in crystal plasticity from a phase-field crystal model.

Area of Science:

• Materials Science
• Condensed Matter Physics
• Computational Materials Science

Background:

• Plastic deformation in single crystals is governed by collective dislocation dynamics.
• Understanding defect behavior is crucial for predicting material properties under stress.

Purpose of the Study:

• To investigate plastic deformation mechanisms in sheared single crystals using a 2D phase-field crystal model.
• To analyze the statistical properties of dislocation population fluctuations and their relation to plastic strain rate.

Main Methods:

• Utilized a two-dimensional phase-field crystal (PFC) model.
• Simulated sheared single crystals to observe dislocation dynamics.
• Analyzed dislocation number fluctuations and plastic strain-rate fluctuations.
• Investigated power-law spectral density and probability distributions of defect populations.

Main Results:

• Identified intermittent fluctuations in dislocation population correlating with bursts in plastic strain rate.
• Observed a power-law spectral density (1/f2) for dislocation number fluctuations at high frequencies.
• Found that probability distributions become bimodal at low driving rates, indicating alternating low and high defect densities.

Conclusions:

• The study reveals a connection between collective dislocation dynamics and intermittent plastic deformation.
• A proposed stochastic model successfully captures the observed statistical properties of dislocation density fluctuations.
• Findings provide insights into defect kinetics governing plastic flow in crystalline materials.