Crossover from Localized to Cascade Relaxations in Metallic Glasses

Fan, Yanqin; Iwashita, Takuya; Egami, T.

doi:10.1103/physrevlett.115.045501

Cited by 104 publications

(84 citation statements)

References 54 publications

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“…Previous studies have shown that the number of energy minima grows exponentially with the average potential energy [28,39]. The increase in the number of minima for rapidly cooled glasses makes them more susceptible to particle rearrangements and increased energy loss [40,41]. Researchers have also shown that more rapidly cooled glasses are more loosely packed and less ordered than slowly cooled glasses [42,43].…”

Section: Resultsmentioning

confidence: 95%

Effects of cooling rate on particle rearrangement statistics: Rapidly cooled glasses are more ductile and less reversible

et al. 2017

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Amorphous solids, such as metallic, polymeric, and colloidal glasses, display complex spatiotemporal response to applied deformations. In contrast to crystalline solids, during loading, amorphous solids exhibit a smooth crossover from elastic response to plastic flow. In this study, we investigate the mechanical response of binary Lennard-Jones glasses to athermal, quasistatic pure shear as a function of the cooling rate used to prepare them. We find several key results concerning the connection between strain-induced particle rearrangements and mechanical response. We show that the energy loss per strain dU loss /dγ caused by particle rearrangements for more rapidly cooled glasses is larger than that for slowly cooled glasses. We also find that the cumulative energy loss U loss can be used to predict the ductility of glasses even in the putative linear regime of stress versus strain. U loss increases (and the ratio of shear to bulk moduli decreases) with increasing cooling rate, indicating enhanced ductility. In addition, we characterized the degree of reversibility of particle motion during a single shear cycle. We find that irreversible particle motion occurs even in the linear regime of stress versus strain. However, slowly cooled glasses, which undergo smaller rearrangements, are more reversible during a single shear cycle than rapidly cooled glasses. Thus, we show that more ductile glasses are also less reversible.

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Section: Resultsmentioning

confidence: 95%

Effects of cooling rate on particle rearrangement statistics: Rapidly cooled glasses are more ductile and less reversible

et al. 2017

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“…All of these models are based on the local structural rearrangement of atoms via the interplay of atomic-scale shear and dilation/contraction in MGs [19][20][21][22][23][24]. Among them, Argon's STZ model involves local rearrangement of a cluster of atoms undergoing a stress-driven, and thermally activated shear distortion [25,23,24].…”

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confidence: 99%

Direct atomic-scale evidence for shear–dilatation correlation in metallic glasses

et al. 2016

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Direct atomic-scale evidence is presented for the shear-dilatation correlation in metallic glasses via molecular dynamics and first-principles calculations. A quantitative parabolic relationship is established between the atomic local shear and hydrostatic volumetric strains by carrying out statistical analysis on a deformed glass model. The correction is further verified by density functional theory. Our atomistic demonstration of shear-dilatation correlation collaborates with the experimentally observed a few percent volume change in shear bands. It brings quantitative insights into the unique correlation between shear transformation and cavitation in metallic glasses.© 2015 Elsevier Ltd. All rights reserved.Metallic glasses (MGs) are a category of promising high strength structural materials with many other superior physical and chemical properties [1]. The deformation mechanisms of such amorphous solid state are in sharp contrast with their crystalline counterparts since there are no long-range atoms packing pattern in MGs [2,3]. No conventional mechanisms, such as ordinary dislocation plasticity or deformation twinning in crystals, exist in MGs which can carry plastic deformation. Therefore MGs usually suffer from the notorious catastrophic failure with a strong strain localization (shear banding) phenomenon [4,5].Several models have been proposed to rationalize the inelastic deformation of MGs, which include free volume [6], shear transformation zone (STZ) [7][8][9], cooperative shear model (CSM) [10,11], flow unit [12], vibrational soft spot [13], shear-diffusive transformation [14,15], and our recently proposed tensile transformation zone (TTZ) [16][17][18]. All of these models are based on the local structural rearrangement of atoms via the interplay of atomic-scale shear and dilation/contraction in MGs [19][20][21][22][23][24]. Among them, Argon's STZ model involves local rearrangement of a cluster of atoms undergoing a stress-driven, and thermally activated shear distortion [25,23,24]. Whereas Spaepen's free volume model is based on a dynamic equilibrium between the stress-assisted creation and annihilation of free volume [6]. The free volume behaviors can be regarded as dilation and contraction of local atomic environments. Since both models have been successfully adopted to describe the homogeneous and inhomogeneous flows in MGs, there should be some intrinsic correlation between shear and dilatation/compaction during deformation of glasses [21,26].Generally, shear-dilatation correlation is an intrinsic nature of deformation in amorphous alloys although local compaction is also allowed [27,28]. For example, intuitively derived law between shear strain and local dilatation has been used in constitutive modelings of MGs [29]. Shear is not necessarily the only deformation mode accommodating the local atomic rearrangement. The microscopic scenario is that the STZ operations redistribute stress spatially which usually leads to the creation of free volume via atomic-scale dilatation [21,1]. So that local ...

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“…So far, we are unaware of any work that has thus far provided a direct link between Eshelby events and aging in metallic glasses, although recent studies have highlighted the important role played by atomic-level stresses. 11,13,32 The decrease in β near Tg reflects the system's close proximity to its equilibrium state (supercooled liquid), where the microscopic dynamics is indeed characterized by stretched exponential correlation functions, in accord with a heterogeneous dynamics scenario. [33][34][35] Upon cooling from the liquid, β increases smoothly and becomes constant, suggesting a continuous evolution from the supercooled liquid to the glassy state.…”

Section: Resultsmentioning

confidence: 85%

“…This type of localized dynamics in metallic glasses has been explored in recent simulation work. 32 Lastly, in order to highlight the deviation of the microscopic dynamics from the expected evolution of the macroscopic τ, we apply a nonlinear relaxation model based on the Tool-Narayanaswamy-Moynihan (TNM) formalism [39][40][41] and compare sets of data taken using a range of macroscopic relaxation techniques with those obtained here using XPCS.…”

Section: Resultsmentioning

confidence: 99%

Comparing the atomic and macroscopic aging dynamics in an amorphous and partially crystalline Zr₄₄Ti₁₁Ni₁₀Cu₁₀Be₂₅bulk metallic glass

et al. 2017

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2Several recent x-ray photon correlation spectroscopy works have reported an anomalous atomic dynamics in hyper-quenched metallic glasses. Here, we compare and contrast these microscopic dynamics with that found in a Zr44Ti11Ni10Cu10Be25 bulk metallic glass, prepared with a cooling rate some 6 orders of magnitude lower. In both cases, structural relaxation in the glass is governed by internal stresses, giving rise to highly compressed density correlation functions. Differently from the fast aging reported in previous studies, here the atomic dynamics displays a slow linear atomic-level aging, while not affecting the shape parameter.Traditional macroscopic phenomenological models fail to capture the temperature dependence of the microscopic structural relaxation time, suggesting a length scale dependence of the aging. Interestingly, the dynamics does not seem to be affected by the presence of a low percentage of frozen in nanocrystals and displays a temperature dependence similar to that observed in macroscopic viscosity measurements.3

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Crossover from Localized to Cascade Relaxations in Metallic Glasses

Cited by 104 publications

References 54 publications

Effects of cooling rate on particle rearrangement statistics: Rapidly cooled glasses are more ductile and less reversible

Effects of cooling rate on particle rearrangement statistics: Rapidly cooled glasses are more ductile and less reversible

Direct atomic-scale evidence for shear–dilatation correlation in metallic glasses

Comparing the atomic and macroscopic aging dynamics in an amorphous and partially crystalline Zr₄₄Ti₁₁Ni₁₀Cu₁₀Be₂₅bulk metallic glass

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Crossover from Localized to Cascade Relaxations in Metallic Glasses

Cited by 104 publications

References 54 publications

Effects of cooling rate on particle rearrangement statistics: Rapidly cooled glasses are more ductile and less reversible

Effects of cooling rate on particle rearrangement statistics: Rapidly cooled glasses are more ductile and less reversible

Direct atomic-scale evidence for shear–dilatation correlation in metallic glasses

Comparing the atomic and macroscopic aging dynamics in an amorphous and partially crystalline Zr44Ti11Ni10Cu10Be25bulk metallic glass

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Comparing the atomic and macroscopic aging dynamics in an amorphous and partially crystalline Zr₄₄Ti₁₁Ni₁₀Cu₁₀Be₂₅bulk metallic glass