Estimation of the shear transformation zone size in a bulk metallic glass through statistical analysis of the first pop-in stresses during spherical nanoindentation

Choi, In-Chul; Zhao, Yakai; Yoo, Byung-Gil; Kim, Yong-Jae; Suh, Jin-Yoo; Ramamurty, Upadrasta; Jang, Jae-il

doi:10.1016/j.scriptamat.2012.02.032

Cited by 100 publications

(35 citation statements)

References 22 publications

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“…However, the precise identification of the b process and STZ remains elusive 16,17 . Different experiments [18][19][20][21] and simulations 5,15,[22][23][24][25][26][27][28] show a large variety of STZ sizes, from few atoms to several hundred. Even similar techniques led to considerably different results.…”

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confidence: 99%

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How thermally activated deformation starts in metallic glass

2014

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The studies on dynamics and deformation in glassy materials are particularly challenging because of their strongly disordered atomic structure. Here, by probing the changes in the atomic displacements and stresses at saddle points of the potential energy landscape, we show that thermally activated deformation is triggered by subnano-scale rearrangements of a small number of atoms, typically less than 10 atoms. The individual triggers are invariant of the cooling history or elastic structure of the system. However, the organizations between different trigger centres can be varied and are related to the overall stability of the system. This finding allows a semi-quantitative construction of the potential energy landscape and brings a new perspective to the study of the mechanical properties of glasses.

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“…Even similar techniques led to considerably different results. For example, in nano-indentation experiments, some studies 21 show the STZ size of few hundred atoms, while others [18][19][20] show a much smaller size around 20 atoms. These remarkable ambiguities in the size and underlying mechanism of the b process are what we seek to clarify in this work.…”

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confidence: 99%

How thermally activated deformation starts in metallic glass

2014

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“…Whereas the atomic level details of STZ still remain elusive, a variety of computer simulations, such as References [3] and [24], made the outline of STZs clearer. The reported size of STZ varies greatly, from 20 to few hundred atoms [21][22][23][24]. However, according to our recent work [25,26], the size of STZ is actually much smaller, involving only about five atoms at the saddle point of the potential energy landscape and about 17 atoms after relaxation from the saddle point to the nearest minimum.…”

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confidence: 99%

Section: Discussionmentioning

confidence: 99%

Deformation in Metallic Glasses Studied by Synchrotron X-Ray Diffraction

Egami

Yang

Dmowski

2016

Metals

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Abstract:High mechanical strength is one of the superior properties of metallic glasses which render them promising as a structural material. However, understanding the process of mechanical deformation in strongly disordered matter, such as metallic glass, is exceedingly difficult because even an effort to describe the structure qualitatively is hampered by the absence of crystalline periodicity. In spite of such challenges, we demonstrate that high-energy synchrotron X-ray diffraction measurement under stress, using a two-dimensional detector coupled with the anisotropic pair-density function (PDF) analysis, has greatly facilitated the effort of unraveling complex atomic rearrangements involved in the elastic, anelastic, and plastic deformation of metallic glasses. Even though PDF only provides information on the correlation between two atoms and not on many-body correlations, which are often necessary in elucidating various properties, by using stress as means of exciting the system we can garner rich information on the nature of the atomic structure and local atomic rearrangements during deformation in glasses.

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“…One mode of deformation in MGs is the spontaneous collective rearrangements of $10-20-atom clusters, [13][14][15][16][17][18] commonly referred to as shear transformation zones (STZs). 19,20 Room-temperature tensile plasticity in metallic glasses is typically nonexistent because in these conditions the STZs strain-soften and coalesce quickly to form shear bands that lead to sample failure.…”

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Ductility and work hardening in nano-sized metallic glasses

Chen

et al. 2015

Applied Physics Letters

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In-situ nano-tensile experiments on 70 nm-diameter free-standing electroplated NiP metallic glass nanostructures reveal tensile true strains of ∼18%, an amount comparable to compositionally identical 100 nm-diameter focused ion beam samples and ∼3 times greater than 100 nm-diameter electroplated samples. Simultaneous in-situ observations and stress-strain data during post-elastic deformation reveal necking and work hardening, features uncharacteristic for metallic glasses. The evolution of free volume within molecular dynamics-simulated samples suggests a free surface-mediated relaxation mechanism in nano-sized metallic glasses.

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Estimation of the shear transformation zone size in a bulk metallic glass through statistical analysis of the first pop-in stresses during spherical nanoindentation

Cited by 100 publications

References 22 publications

How thermally activated deformation starts in metallic glass

How thermally activated deformation starts in metallic glass

Deformation in Metallic Glasses Studied by Synchrotron X-Ray Diffraction

Ductility and work hardening in nano-sized metallic glasses

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