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Abstract
Glass transition is one of the unresolved critical issues in solid-state physics and materials science, during which a viscous liquid is frozen into a solid or structurally arrested state. On account of the uniform arrested mechanism, the calorimetric glass transition temperature (Tg) always follows the same trend as the dynamical glass transition (or α-relaxation) temperature (Tα) determined by dynamic mechanical analysis (DMA). Here, we explored the correlations between the calorimetric and dynamical glass transitions of three prototypical high-entropy metallic glasses (HEMGs) systems. We found that the HEMGs present a depressed dynamical glass transition phenomenon, i.e., HEMGs with moderate calorimetric Tg represent the highest Tα and the maximum activation energy of α-relaxation. These decoupled glass transitions from thermal and mechanical measurements reveal the effect of high configurational entropy on the structure and dynamics of supercooled liquids and metallic glasses, which are associated with sluggish diffusion and decreased dynamic and spatial heterogeneities from high mixing entropy. The results have important implications in understanding the entropy effect on the structure and properties of metallic glasses for designing new materials with plenteous physical and mechanical performances.
Highlights
Glass transition is one of the unresolved critical issues in solid-state physics and materials science, during which a viscous liquid is frozen into a solid or structurally arrested state
From a dynamical relaxation perspective, diverse relaxation responses emerge with increasing temperature, from local reversible β-relaxation to global irreversible α-relaxation or a dynamic glass transition that is accompanied by the activation and subsequent percolation of shear transformation zones (STZs)[11,12,13,14]
We utilized the strategy of the equivalent substitution elements to design La(Ce)-based, Pd(Pt)-based, and Ti (Zr)-based Metallic glass (MG) and high-entropy metallic glasses (HEMGs), as the model systems to investigate the high-entropy effect on the structure and dynamics of glassforming alloys
Summary
Glass transition is one of the unresolved critical issues in solid-state physics and materials science, during which a viscous liquid is frozen into a solid or structurally arrested state. We found that the HEMGs present a depressed dynamical glass transition phenomenon, i.e., HEMGs with moderate calorimetric Tg represent the highest Tα and the maximum activation energy of α-relaxation These decoupled glass transitions from thermal and mechanical measurements reveal the effect of high configurational entropy on the structure and dynamics of supercooled liquids and metallic glasses, which are associated with sluggish diffusion and decreased dynamic and spatial heterogeneities from high mixing entropy. Inheriting the distinct properties of MGs and HEAs, the new combinative glass-formed systems termed as “high entropy metallic glasses (HEMGs)” present high thermostability with depressed crystallization kinetics and superior magnetic properties, which reflect the theme of “more is different”[34,35,36]. We utilized the strategy of the equivalent substitution elements to design La(Ce)-based, Pd(Pt)-based, and Ti (Zr)-based MGs and HEMGs, as the model systems to investigate the high-entropy effect on the structure and dynamics of glassforming alloys
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