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Methods of Ex Situ and In Situ Investigations of Structural Transformations: The Case of Crystallization of Metallic Glasses
Published on: June 7, 2018
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Sub-T(g) relaxation patterns in Cu-based metallic glasses far from equilibrium
Caiwei Wang1, Lina Hu1, Chen Wei1
1Key Laboratory for Liquid-Solid Structural Evolution and Processing of Materials (Ministry of Education), Shandong University, Jinan 250061, China.
The Journal of Chemical Physics
|November 3, 2014
Summary
Cu-based metallic glasses exhibit abnormal three-stage sub-T(g) relaxation patterns, linked to non-monotonic cluster size changes and potential liquid-liquid phase transitions in supercooled liquids.
Area of Science:
- Materials Science
- Condensed Matter Physics
- Physical Chemistry
Background:
- Sub-glass-transition (sub-T(g)) relaxation patterns (RPs) are crucial for understanding the behavior of metallic glasses.
- Cu-based glass ribbons (GRs) are technologically relevant materials whose relaxation dynamics are not fully understood.
Purpose of the Study:
- To investigate the sub-T(g) relaxation patterns in binary and quaternary Cu-based glass ribbons.
- To elucidate the structural and dynamic evolution in liquids associated with observed three-stage sub-T(g) relaxation processes.
- To determine the factors influencing abnormal relaxation behavior in metallic glasses.
Main Methods:
- Utilized a hyperquenching-sub-T(g) annealing-calorimetric approach.
- Analyzed relaxation patterns in binary and quaternary Cu-based glass ribbons.
- Investigated structural evolution from superheated to supercooled liquids.
Main Results:
- The abnormal three-stage relaxation behavior is not universal for Cu-based metallic glasses and cannot be predicted solely by enthalpy of mixing.
- This abnormal RP correlates with non-monotonic changes in cluster size and medium-range order in supercooled liquids.
- An anomalous viscosity drop during cooling in superheated liquids, indicative of a liquid-liquid phase transition, is linked to the unusual structural changes causing the observed relaxation patterns.
Conclusions:
- The study reveals that abnormal three-stage sub-T(g) RPs in Cu-based GRs are associated with specific structural dynamics, not general alloy properties.
- Non-monotonic changes in cluster size and medium-range order are key factors in these abnormal relaxation behaviors.
- Evidence suggests a liquid-liquid phase transition in superheated liquids may be a signature of the structural evolution leading to these unique relaxation patterns.
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