skip to main content
US FlagAn official website of the United States government
dot gov icon
Official websites use .gov
A .gov website belongs to an official government organization in the United States.
https lock icon
Secure .gov websites use HTTPS
A lock ( lock ) or https:// means you've safely connected to the .gov website. Share sensitive information only on official, secure websites.

Explore Research Products in the PAR
It may take a few hours for recently added research products to appear in PAR search results.


Title: A Perspective on Metallic Liquids and Glasses
Metallic glasses have the potential to become transformative materials, but this is hindered by the lack of ability to accurately predict which metallic alloys will form good glasses. Current approaches are limited to empirical rules that often rely on parameters that are unknown until the glasses are made, rendering them not predictive. In this Perspective, properties of metallic liquids at elevated temperatures and how these might lead to better predictions for glass formation are explored. A central topic is liquid fragility, which characterizes the different dynamics of the liquids. What fragility is and how it might be connected to the liquid structure is discussed. Since glass formation is ultimately limited by crystallization during cooling, recent advances in crystal growth and nucleation are also reviewed. Finally, some approaches for improving glass stability and glass rejuvenation for improved plasticity are discussed. Building on a summary of results, some key questions are raised and a prospective for future studies is offered.  more » « less
Award ID(s):
1904281
PAR ID:
10545825
Author(s) / Creator(s):
Publisher / Repository:
American Institute of Physics
Date Published:
Journal Name:
Journal of applied physics
Volume:
134
Issue:
1
ISSN:
0021-8979
Page Range / eLocation ID:
010902
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
More Like this
  1. ; ; ; ; ; ; ; ; ; (, Nature Communications)
    Abstract The viscosity and its temperature dependence, the fragility, are key properties of a liquid. A low fragility is believed to promote the formation of metallic glasses. Yet, the fragility remains poorly understood, since experimental data of its compositional dependence are scarce. Here, we introduce the film inflation method (FIM), which measures the fragility of metallic glass forming liquids across wide ranges of composition and glass-forming ability. We determine the fragility for 170 alloys ranging over 25 at.% in Mg–Cu–Y. Within this alloy system, large fragility variations are observed. Contrary to the general understanding, a low fragility does not correlate with high glass-forming ability here. We introduce crystallization complexity as an additional contribution, which can potentially become significant when modeling glass forming ability over many orders of magnitude. 
    more » « less
  2. ; (, Applied Physics Letters)
    The surface diffusion kinetics on a Pd77.5Cu6Si16.5 metallic glass is measured using a scratch smoothing method in the range of 107–57 K below the glass transition temperature. Within this temperature range, the surface diffusion coefficients are determined to vary between (8.66 ± 0.80) × 10−19 and (5.90 ± 0.60) × 10−18 m2 s−1. The corresponding activation energy is 0.93 ± 0.18 eV, which is about half the value for bulk diffusion. These measurements also corroborate the correlation between enhanced surface diffusion and liquid fragility in glasses. 
    more » « less
  3. ; ; ; ; ; (, Nature Communications)
    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 ( T g ) always follows the same trend as the dynamical glass transition (or α -relaxation) temperature ( T α ) 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 T g represent the highest T α 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. 
    more » « less
  4. ; ; ; (, Communications Chemistry)
    Abstract The potential energy landscape (PEL) formalism is a powerful tool within statistical mechanics to study the thermodynamic properties of classical low-temperature liquids and glasses. Recently, the PEL formalism has been extended to liquids/glasses that obey quantum mechanics, but applications have been limited to atomistic model liquids. In this work, we extend the PEL formalism to liquid/glassy water using path-integral molecular dynamics (PIMD) simulations, where nuclear quantum effects (NQE) are included. Our PIMD simulations, based on the q-TIP4P/F water model, show that the PEL of quantum water is both Gaussian and anharmonic. Importantly, the ring-polymers associated to the O/H atoms in the PIMD simulations, collapse at the local minima of the PEL (inherent structures, IS) for both liquid and glassy states. This allows us to calculate, analytically, the IS vibrational density of states (IS-VDOS) of the ring-polymer system using the IS-VDOS of classical water (obtained from classical MD simulations). The role of NQE on the structural properties of liquid/glassy water at various pressures are discussed in detail. Overall, our results demonstrate that the PEL formalism can effectively describe the behavior of molecular liquids at low temperatures and in the glass states, regardless of whether the liquid/glass obeys classical or quantum mechanics. 
    more » « less
  5. ; ; ; (, Proceedings of the National Academy of Sciences)
    An experimental study of the configurational thermodynamics for a series of near-eutectic Pt80-xCuxP20bulk metallic glass-forming alloys is reported where 14 <x< 27. The undercooled liquid alloys exhibit very high fragility that increases asxdecreases, resulting in an increasingly sharp glass transition. With decreasingx, the extrapolated Kauzmann temperature of the liquid,TK, becomes indistinguishable from the conventionally defined glass transition temperature,Tg. Forx< 17, the observed liquid configurational enthalpy vs.Tdisplays a marked discontinuous drop or latent heat at a well-defined freezing temperature,Tgm. The entropy drop for this first-order liquid/glass transition is approximately two-thirds of the entropy of fusion of the crystallized eutectic alloy. BelowTgm, the configurational entropy of the frozen glass continues to fall rapidly, approaching that of the crystallized eutectic solid in the low T limit. The so-called Kauzmann paradox, with negative liquid entropy (vs. the crystalline state), is averted and the liquid configurational entropy appears to comply with the third law of thermodynamics. Despite their ultrafragile character, the liquids atx= 14 and 16 are bulk glass formers, yielding fully glassy rods up to 2- and 3-mm diameter on water quenching in thin-wall silica tubes. The low Cu content alloys are definitive examples of glasses that exhibit first-order melting. 
    more » « less
  • Citation Formats
  • MLA
  • APA
  • Chicago
  • BibTeX
  • Save / Share this Record
  • Send to Email