Density changes in shear bands of a metallic glass determined by correlative analytical transmission electron microscopy

Rösner, Harald; Peterlechner, Martin; Kübel, Christian; Schmidt, Volkmar; Wilde, Gerhard

doi:10.1016/j.ultramic.2014.03.006

Cited by 132 publications

(135 citation statements)

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“…It indicates that there is indeed strong correlation between shear, non-affine displacement, and dilatation at atomic-scale. It is also interesting to notice both atomic dilatation and contraction if one carefully check the volumetric coloring scheme, which agrees with latest experimental observations [27,28]. In Fig.…”

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confidence: 88%

“…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].…”

mentioning

confidence: 99%

“…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].…”

mentioning

confidence: 99%

“…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 structural dilatation [19,30,31], density change [27,28], and even nanovoids [32,33,21,34] have been observed within the shear bands of MGs. Although the concept of shear-dilatation correlation is widely accepted in the glass community, and various experiments and simulations have indicated STZ and cavitation as important deformation and fracture mechanisms of glassy alloys [33,35,31,18,17,34], there still lacks a direct microscopic evidence and no quantitative relationship established for such an intimate correlation.…”

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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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confidence: 99%

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

et al. 2016

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“…It has been applied e.g. for the local analysis of shear bands in metallic glasses [20] [21]. However, the interpretation of the abstract diffraction variations is not straightforward and usually requires supplementary simulations, such as reverse Monte Carlo modeling [22].…”

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confidence: 99%

Radial distribution function imaging by STEM diffraction: Phase mapping and analysis of heterogeneous nanostructured glasses

Wang

Feng

et al. 2016

Ultramicroscopy

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To overcome some of the challenges in characterizing heterogeneous nanostructured amorphous materials, we developed a new TEM method, RDF imaging, combining scanning transmission electron microscopy diffraction mapping with radial distribution function (RDF) analysis followed by hyperspectral analysis, to enable phase analysis and mapping of heterogeneous amorphous structures purely based on their short-and medium range atomic order. We applied this method to an amorphous zirconium oxide and zirconium iron multilayer system, demonstrating an extreme sensitivity of the method to small atomic packing variations. This approach has great potential to understand local structure variations in glassy composite materials and to provide new insights to correlate structure and properties of glasses.

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Strain Gradient in Micro‐Hardness Testing and Structural Relaxation in Metallic Glasses

Champion

Perrière

2014

Adv Eng Mater

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An analytical model is proposed to quantitatively describe the depth-dependence of Vickers microhardness in metallic glasses. The approach is based on a shear bands distribution-induced strain gradient during testing and was used to analyze thermal relaxation in the Zr Mg 65 Cu 12.5 Ni 12.5 MM 10 metallic glasses. It was shown that a decrease of the free volume leads systematically to a decrease of the alloy hardness. This analysis also gives an evaluation of the shear band thickness and the role of the elastic properties in the depth-dependence of the Vickers micro-hardness.

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Density changes in shear bands of a metallic glass determined by correlative analytical transmission electron microscopy

Cited by 132 publications

References 48 publications

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

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

Radial distribution function imaging by STEM diffraction: Phase mapping and analysis of heterogeneous nanostructured glasses

Strain Gradient in Micro‐Hardness Testing and Structural Relaxation in Metallic Glasses

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