Relaxation Decoupling in Metallic Glasses at Low Temperatures

Area of Science:

• Materials Science
• Condensed Matter Physics
• Physical Chemistry

Background:

• Glass-forming liquids exhibit dynamic decoupling between fast beta (β) and slow alpha (α) relaxation processes upon cooling.
• This phenomenon significantly impacts the understanding of glass physics and material properties.
• Previous studies have focused on distinct relaxation processes, but the transition between them remains an area of interest.

Purpose of the Study:

• To investigate the evolution of relaxation profiles in metallic glasses across an extensive range of temperatures and timescales.
• To identify and characterize the dynamic decoupling of relaxation processes in the glass state.
• To correlate observed relaxation behaviors with underlying microscopic and large-scale dynamics.

Main Methods:

• Experimental exploration of metallic glasses over a wide temporal and temperature range.
• Analysis of relaxation profiles to identify changes from single-step to two-step decay.
• Correlation of relaxation dynamics with stress-dominated microscopic motion and subdiffusive motion.

Main Results:

• A surprising gradual transition from single-step to two-step relaxation decay was observed upon cooling in various metallic glasses.
• This transition suggests a decoupling of relaxation into two distinct processes within the glass state.
• The faster process is linked to anomalous stress-dominated microscopic dynamics, while the slower process involves subdiffusive motion at larger scales.

Conclusions:

• The study reveals a novel gradual decoupling of relaxation dynamics in metallic glasses, challenging previous assumptions of abrupt transitions.
• The findings provide insights into the coexistence of distinct dynamic processes governing the behavior of glasses.
• This work contributes to a deeper understanding of the complex dynamics governing glass-forming liquids and their transition to the glassy state.