The role of time in activation of flow units in metallic glasses

Ge, T. P.; Gao, Xuesong; Huang, Bo; Wang, W.H.; Bai, H. Y.

doi:10.1016/j.intermet.2015.07.004

Cited by 19 publications

(4 citation statements)

References 43 publications

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“…Large fractions of the sample exhibit a liquid-like behavior when exposed to external stress fields with slower strain rates. The different strain rates can actually resale the cut-off position of the dynamics limit of flow units, and the slower strain rate with a longer observing time will push the dynamic limit to the slower side [ 111 ]. Remarkably, the fraction of flow units needs to overpass the connectivity percolation threshold ∼0.25 before yielding at ∼3% strain, to achieve steady stable flowing.…”

Section: Properties Of Flow Units and Their Evolution Under External Fieldsmentioning

confidence: 99%

Flow units as dynamic defects in metallic glassy materials

Wang

2018

National Science Review

115

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In a crystalline material, structural defects such as dislocations or twins are well defined and largely determine the mechanical and other properties of the material. For metallic glass (MG) with unique properties in the absence of a long-range lattice, intensive efforts have focused on the search for similar ‘defects’. The primary objective has been the elucidation of the flow mechanism of MGs. However, their atomistic mechanism of mechanical deformation and atomic flow response to stress, temperature, and failure, have proven to be challenging. In this paper, we briefly review the state-of-the-art studies on the dynamic defects in metallic glasses from the perspective of flow units. The characteristics, activation and evolution processes of flow units as well as their correlation with mechanical properties, including plasticity, strength, fracture, and dynamic relaxation, are introduced. We show that flow units that are similar to structural defects such as dislocations are crucial in the optimization and design of metallic glassy materials via the thermal, mechanical and high-pressure tailoring of these units. In this report, the relevant issues and open questions with regard to the flow unit model are also introduced and discussed.

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Section: Properties Of Flow Units and Their Evolution Under External Fieldsmentioning

confidence: 99%

Flow units as dynamic defects in metallic glassy materials

Wang

2018

National Science Review

115

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“…Previous work 12,31,[50][51][52] and this work show that the loading time or the observation time, equivalent to temperature and stress, is one of the key parameters to glass transition or plastic deformation in MGs, and the change of any of them has equivalent role in glass transition or plastic deformation. So, a diagram of the flow for both plastic deformation and glass to liquid transformation of a MG can be constructed as shown in Fig.…”

Section: Resultsmentioning

confidence: 70%

“…And this is the intrinsic reason for the time dependent properties of the MG. The relation of the volume fraction of flow units c and the loading time (equivalent to the observation time) t of the MG can be estimated as 50…”

Section: Resultsmentioning

confidence: 99%

Evolution of structural and dynamic heterogeneities during elastic to plastic transition in metallic glass

Zhao

Xue

et al. 2015

Journal of Applied Physics

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We investigate the evolution of microscopically localized flow under a constant applied strain in apparent elastic region of a prototypical metallic glass (MG). The distribution and evolution of energy barriers and relaxation time spectra of the activated flow units in MG with time are obtained via activation-relaxation method. The results show that the unstable nano-scale liquid-like regions acting as flow units in the glass can be activated by external stress, and their evolution with time shows a crossover from localized activation to cascade as the proportion of the flow units reaches a critical percolation value. The flow unit evolution leads to a mechanical elastic-to-plastic transition or macroscopic plastic flow. A plausible diagram involved in time, stress, and temperature is established to understand the deformations and the flow mechanisms of MGs and could provide insights on the intriguing dilemmas of glassy nature, the flow units, and their correlations with the deformation behaviors in MGs. V

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“…Both simulations and experiments have revealed that relaxation [34], yield [35,36], glass transition [32] and crystallization [37] of MGs were closely related to the structural heterogeneity or "flow unit". Although plastic deformability of MG was also reported to may be controlled by the structural heterogeneity like that of the dislocations to crystalline material [31,33,38], the physical correlation between intrinsic atomic-scale structural heterogeneity and the macroscopic spatiotemporal inhomogeneous dynamics of serrated plastic flow behavior is still unclear.…”

Section: Introductionmentioning

confidence: 99%

Effect of structural heterogeneity on serrated flow behavior of Zr-based metallic glass

Liu

Huan

et al. 2018

Journal of Alloys and Compounds

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Physical correlation between structural heterogeneity and plastic flow of metallic glasses (MGs) is crucial for the understanding of MGs' deformation mechanism. In this work, different degrees of structural heterogeneity are introduced into Zr-based MGs through different cooling rates casting. The effect of structural heterogeneity on serrated flow behavior was studied. The findings demonstrate that there exists a tendency that serration flow dynamics of the MGs transforms from a chaotic state to a selforganized critical state with increased inhomogeneity. The established correlation between structural heterogeneity and serrated flow behavior shows that the higher degree of structural heterogeneity facilitates a higher frequency of interaction and multiplication of shear bands by increasing nucleation sites, and then promotes serrated flow behavior to be more homogeneous in time and space, thereby induces transformation of dynamics behavior and improves the plasticity. The obtained results shed light on deformation mechanism of plastic flow and provide a new insight into the plasticity of MGs.

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The role of time in activation of flow units in metallic glasses

Cited by 19 publications

References 43 publications

Flow units as dynamic defects in metallic glassy materials

Flow units as dynamic defects in metallic glassy materials

Evolution of structural and dynamic heterogeneities during elastic to plastic transition in metallic glass

Effect of structural heterogeneity on serrated flow behavior of Zr-based metallic glass

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