Vitrification decoupling from α-relaxation in a metallic glass.

Area of Science:

• Materials Science
• Condensed Matter Physics
• Physical Chemistry

Background:

• Vitrification, the process of forming glasses, is a fundamental phenomenon in materials science.
• Understanding the kinetics of vitrification and its relationship with atomic mobility is crucial for designing new materials.
• The established view links glass transition directly to the alpha-relaxation dynamics of atoms.

Purpose of the Study:

• To investigate the vitrification kinetics and atomic mobility in an Au-based bulk metallic glass.
• To challenge the conventional one-to-one correlation between vitrification and alpha-relaxation.
• To explore the role of other atomic motions in the vitrification process.

Main Methods:

• Fast scanning calorimetry was employed to study vitrification kinetics and alpha-relaxation.
• Analysis focused on the limiting fictive temperature and the time scale of atomic mobility.
• Experimental data were compared to theoretical expectations for fragile liquids.

Main Results:

• The alpha-relaxation in the metallic glass exhibits a super-Arrhenius temperature dependence, characteristic of fragile liquids.
• Vitrification kinetics show a weaker temperature dependence at moderate undercooling.
• Vitrification occurs at temperatures below those associated with alpha-relaxation.

Conclusions:

• The study challenges the direct correlation between vitrification and alpha-relaxation, suggesting a more complex mechanism.
• At moderate to deep undercooling, atomic motions beyond alpha-relaxation contribute significantly to vitrification.
• These findings have implications for understanding the fundamental properties of glasses and metallic glasses.