Unusual fast secondary relaxation in metallic glass

Wang, Q.; Zhang, S.T.; Yang, Yong; Dong, Yuecheng; Liu, C.T.; J, Lu

doi:10.1038/ncomms8876

Cited by 171 publications

(83 citation statements)

References 43 publications

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“…The atomic scenario of the slow event is actually the percolation of the local atomic rearrangement with a critical role of atomic diffusion [35,53,54], which is a thermally activated process at a low stress level that needs a longer time to be excited. The above scenario of the local atomic rearrangement and the long-range diffusion in stress relaxation is in accordance with the hypothesized atomic pictures of a recently discovered unusual ultrafast and usual fast β relaxation in MGs [55]. Here we further provide an atomic-scale evidence for the fast stress-driven, and slow thermally activated processes during stress relaxation of MGs.…”

Section: B Atomistic Understanding Of Stress Relaxationsupporting

confidence: 59%

Transition from stress-driven to thermally activated stress relaxation in metallic glasses

et al. 2016

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The short-range ordered, but long-range disordered structure of metallic glasses yields strong structural and dynamic heterogeneities. Stress relaxation is a technique to trace the evolution of stress in response to a fixed strain, which reflects the dynamic features phenomenologically described by the Kohlrausch-Williams-Watts (KWW) equation. The KWW equation describes a broad distribution of relaxation times with a small number of empirical parameters, but it does not arise from a particular physically motivated mechanistic picture. Here we report an anomalous two-stage stress relaxation behavior in a Cu 46 Zr 46 Al 8 metallic glass over a wide temperature range and generalize the findings in other compositions. Thermodynamic analysis identifies two categories of processes: a fast stress-driven event with large activation volume and a slow thermally activated event with small activation volume, which synthetically dominates the stress relaxation dynamics. Discrete analyses rationalize the transition mechanism induced by stress and explain the anomalous variation of the KWW characteristic time with temperature. Atomistic simulations reveal that the stress-driven event involves virtually instantaneous short-range atomic rearrangement, while the thermally activated event is the percolation of the fast event accommodated by the long-range atomic diffusion. The insights may clarify the underlying physical mechanisms behind the phenomenological description and shed light on correlating the hierarchical dynamics and structural heterogeneity of amorphous solids.

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Section: B Atomistic Understanding Of Stress Relaxationsupporting

confidence: 59%

Transition from stress-driven to thermally activated stress relaxation in metallic glasses

et al. 2016

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“…From the perspective of PEL, a potential nano-scale flow event, which is localized and confined by surrounding atoms, corresponds to the b-mode flow or b-relaxation; by contrast, the percolation of the flow units, entailing large scale atomic migration and irreversible structural change, leads to macroscopic yielding and plastic flow which corresponds to the amode flow or a-relaxation [51]. Recently, Wang et al [52] further discovered a faster secondary relaxation (b 0 relaxation) in a LaeCebased metallic glass in addition to the conventional b-relaxation.…”

Section: Thermal Activation and Mechanical Relaxationmentioning

confidence: 99%

On the source of plastic flow in metallic glasses: Concepts and models

et al. 2015

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a b s t r a c tWe briefly review the state-of-the-art study on plastic flow in metallic glasses. Especially, we survey the features and behaviors, percolation, and response of the basic deformation units to the activation of stress and temperature, and various models and notions on microscopic flow in metallic glasses. The discussion, comments and perspective on possible unified notation, terminologies and models on plastic flow in metallic glasses are presented. The purpose is to reach a consensus within the community with a hope to eventually unify the notations and models on the deformations in metallic glasses.

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“…Despite a simple atomic structure, MGs can exhibit more than one mode of bulk b-relaxation, 16 attributed to different mobility of different atom pairs. Despite a simple atomic structure, MGs can exhibit more than one mode of bulk b-relaxation, 16 attributed to different mobility of different atom pairs.…”

Section: Introductionmentioning

confidence: 99%

Composition-dependent metallic glass alloys correlate atomic mobility with collective glass surface dynamics

Nguyễn

Zhu

Pringle

et al. 2016

Phys. Chem. Chem. Phys.

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Glassy metallic alloys are richly tunable model systems for surface glassy dynamics. Here we study the correlation between atomic mobility, and the hopping rate of surface regions (clusters) that rearrange collectively on a minute to hour time scale. Increasing the proportion of low-mobility copper atoms in La-Ni-Al-Cu alloys reduces the cluster hopping rate, thus establishing a microscopic connection between atomic mobility and dynamics of collective rearrangements at a glass surface made from freshly exposed bulk glass. One composition, La60Ni15Al15Cu10, has a surface resistant to re-crystallization after three heating cycles. When thermally cycled, surface clusters grow in size from about 5 glass-forming units to about 8 glass-forming units, evidence of surface aging without crystal formation, although its bulk clearly forms larger crystalline domains. Such kinetically stable glass surfaces may be of use in applications where glassy coatings stable against heating are needed.

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Unusual fast secondary relaxation in metallic glass

Cited by 171 publications

References 43 publications

Transition from stress-driven to thermally activated stress relaxation in metallic glasses

Transition from stress-driven to thermally activated stress relaxation in metallic glasses

On the source of plastic flow in metallic glasses: Concepts and models

Composition-dependent metallic glass alloys correlate atomic mobility with collective glass surface dynamics

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