Strain-driven Kovacs-like memory effect in glasses

Area of Science:

• Materials Science
• Condensed Matter Physics
• Rheology

Background:

• Understanding complex relaxation behaviors is crucial for characterizing the nature of glasses.
• Glasses exhibit unique mechanical properties due to their disordered atomic structures.

Purpose of the Study:

• To investigate and report a Kovacs-like memory effect in glasses.
• To explore the factors influencing this memory effect and its underlying physical origins.

Main Methods:

• Two-step high-to-low strain stimulations were applied to glassy materials.
• Stress relaxation processes were monitored.
• In-situ synchrotron X-ray experiments were conducted.
• Relaxation kinetics were analyzed.

Main Results:

• A non-monotonic stress relaxation, characterized by an initial increase followed by a decrease, was observed after a strain jump from a higher to a lower state.
• The observed memory effect intensified with increased strain in the first stage, higher temperatures, and longer stimulation durations, correlating with highly collective atomic motions and larger activation energies.
• Synchrotron X-ray data provided insights into the physical mechanisms driving the stress memory effect.

Conclusions:

• The study demonstrates a Kovacs-like memory effect in glasses, highlighting complex relaxation dynamics.
• The findings suggest that this stress memory effect is likely a universal phenomenon across various types of glasses.
• The research deepens the understanding of glass behavior and relaxation kinetics.