Dislocation mutual interactions mediated by mobile impurities and the conditions for plastic instabilities

Area of Science:

• Materials Science
• Condensed Matter Physics
• Solid Mechanics

Background:

• Metallic alloys exhibit plastic instabilities, known as the Portevin-Le Chatelelier effect, characterized by serrated stress-strain curves.
• This serration arises from the dynamic interaction between dislocations and solute atoms, leading to discontinuous material deformation.

Purpose of the Study:

• To investigate the fundamental mechanisms driving serration in metallic alloys.
• To develop a theoretical framework for predicting the onset and characteristics of the Portevin-Le Chatelelier effect.
• To elucidate the role of dislocation interactions in the observed plastic instabilities.

Main Methods:

• Development of a simplified model for interacting dislocations.
• Application of the classical Einstein fluctuation-dissipation relation to define temperature within the model.
• Analytical calculations and numerical integration of equations of motion.

Main Results:

• Successful definition of temperature across a range of model parameters.
• Construction of a phase diagram for serration behavior, comparable to experimental data.
• Clarification of the significant contribution of mutual dislocation interactions to serration phenomena.

Conclusions:

• The study provides a robust theoretical model for understanding serration in metallic alloys.
• The fluctuation-dissipation relation offers a novel approach to characterizing temperature effects in plastic instabilities.
• Mutual dislocation interactions are identified as a critical factor governing the Portevin-Le Chatelelier effect.