From elastic excitations to macroscopic plasticity in metallic glasses

Şopu, Daniel; Yuan, Xingliang; Moitzi, Franco; Spieckermann, Florian; Bian, Xilei; Eckert, Jürgen

doi:10.1016/j.apmt.2021.100958

Cited by 16 publications

(21 citation statements)

References 42 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Due to the existence of earlier activated STZs, lower stress is needed for the formation of plastic zones, which finally leads to lower yield stress compared to sample 1. Nevertheless, the

relaxation is the locally string-like dynamic behavior of atoms [ 38 , 41 , 42 ] and, hence, localized deformation can still be seen in sample 2, as highlighted in Figure 1 d. Finally, in sample 3 and sample 4, although these two tested systems are picked at different dilution levels, in both, the activated

relaxation is driven by atoms of high mobility. Eventually, a homogeneous deformation mechanism instead of localized shear deformation can be seen in these two samples (see Figure 1 e,f).…”

Section: Resultsmentioning

confidence: 93%

“…The smooth slope in the stress–strain curve of sample 2 compared to sample 1 highlights a more homogeneous deformation mode. At this point, the

relaxation is pronounced due to the excess free volume which can be associated with the activation of a large number of shear transformation zones (STZs) [ 38 , 39 , 40 ]. Due to the existence of earlier activated STZs, lower stress is needed for the formation of plastic zones, which finally leads to lower yield stress compared to sample 1.…”

Section: Resultsmentioning

confidence: 99%

See 1 more Smart Citation

Relaxation and Strain-Hardening Relationships in Highly Rejuvenated Metallic Glasses

et al. 2022

View full text Add to dashboard Cite

One way to rejuvenate metallic glasses is to increase their free volume. Here, by randomly removing atoms from the glass matrix, free volume is homogeneously generated in metallic glasses, and glassy states with different degrees of rejuvenation are designed and further mechanically tested. We find that the free volume in the rejuvenated glasses can be annihilated under tensile or compressive deformation that consequently leads to structural relaxation and strain-hardening. Additionally, the deformation mechanism of highly rejuvenated metallic glasses during the uniaxial loading–unloading tensile tests is investigated, in order to provide a systematic understanding of the relaxation and strain-hardening relationship. The observed strain-hardening in the highly rejuvenated metallic glasses corresponds to stress-driven structural and residual stress relaxation during cycling deformation. Nevertheless, the rejuvenated metallic glasses relax to a more stable state but could not recover their initial as-cast state.

show abstract

“…Due to the existence of earlier activated STZs, lower stress is needed for the formation of plastic zones, which finally leads to lower yield stress compared to sample 1. Nevertheless, the

relaxation is driven by atoms of high mobility. Eventually, a homogeneous deformation mechanism instead of localized shear deformation can be seen in these two samples (see Figure 1 e,f).…”

Section: Resultsmentioning

confidence: 93%

“…The smooth slope in the stress–strain curve of sample 2 compared to sample 1 highlights a more homogeneous deformation mode. At this point, the

Section: Resultsmentioning

confidence: 99%

Relaxation and Strain-Hardening Relationships in Highly Rejuvenated Metallic Glasses

et al. 2022

View full text Add to dashboard Cite

show abstract

“…A better view of the shear band interaction mechanism is given by the sign of the rotation angle, generally used to identify vortex-like (rotating) units in glassy structures (Fig. 4b) [33,34]. The sign of rotation defines the shear direction and has high implication on the dynamics of shear band interaction.…”

Section: S2mentioning

confidence: 99%

“…The sign of rotation defines the shear direction and has high implication on the dynamics of shear band interaction. When two shear bands intersect, vortexes of opposite rotation directions come into contact and the further movement of the shear bands is hindered [34]. This process blocks the initial shear front and changes the shear band dynamics and morphology, ultimately leading to shear band blocking, branching and multiplication [33].…”

Section: S2mentioning

confidence: 99%

Rejuvenation engineering in metallic glasses by stress and structure modulation

Şopu¹,

Spieckermann²,

Bian³

et al. 2022

Preprint

Self Cite

View full text Add to dashboard Cite

Residual stress engineering is very widely used in the design of new advanced lightweight materials. For metallic glasses the attention has been on structural changes and rejuvenation processes.High energy scanning X-ray diffraction strain mapping reveals large elastic fluctuations in metallic glasses after deformation under triaxial compression. Transmission electron microscopy proves that structural rejuvenation under room temperature deformation relates to the shear band formation that closely correlates to the underlying distribution of elastic heterogeneities. Microindentation hardness mapping hints at an unsymmetrical hardening/softening after compression and further reveals the competing effects of elastic fluctuations and structure modulation. Molecular dynamics simulations provide an atomistic understanding of the correlation between shear banding and fluctuations in the local strain/stress heterogeneity. Thus, future focus should be given to stress engineering and elastic heterogeneity that together with structure modulation may allow to design metallic glasses with enhanced ductility and strain hardening ability.

show abstract

“…Atomic-level simulations, which can numerically inspect the strain evolution and local atomic rearrangement in cubes with dimensions of a few tens of nanometers and over time scales of nanoseconds at a high deformation rate, have been employed extensively to study the shear banding process. [5][6][7][8][9] Experimentally, only a few electron microscopy and atomic probe tomography investigations, which provide the spatial resolution necessary for resolving nanoscale features, have been devoted to directly investigate the structure and chemistry of individual shear bands. [10][11][12][13][14] Using scanning transmission electron microscopy (STEM) annular dark field (ADF) imaging, Maaß et al observed a reduction in scattering power at the core of shear bands suggesting spatially localized free volume, [10] while Rösner et al observed alternating scattering power along shear bands, which have been associated with local density fluctuations.…”

Section: Introductionmentioning

confidence: 99%

Direct Observation of Quadrupolar Strain Fields forming a Shear Band in Metallic Glasses

et al. 2023

View full text Add to dashboard Cite

For decades, scanning/transmission electron microscopy (S/TEM) techniques have been employed to analyze shear bands in metallic glasses and understand their formation in order to improve the mechanical properties of metallic glasses. However, due to a lack of direct information in reciprocal space, conventional S/TEM cannot characterize the local strain and atomic structure of amorphous materials, which are key to describe the deformation of glasses. For this work, 4-dimensional-STEM (4D-STEM) is applied to map and directly correlate the local strain and the atomic structure at the nanometer scale in deformed metallic glasses. Residual strain fields are observed with quadrupolar symmetry concentrated at dilated Eshelby inclusions. The strain fields percolate in a vortex-like manner building up the shear band. This provides a new understanding of the formation of shear bands in metallic glass.

show abstract

From elastic excitations to macroscopic plasticity in metallic glasses

Cited by 16 publications

References 42 publications

Relaxation and Strain-Hardening Relationships in Highly Rejuvenated Metallic Glasses

Relaxation and Strain-Hardening Relationships in Highly Rejuvenated Metallic Glasses

Rejuvenation engineering in metallic glasses by stress and structure modulation

Direct Observation of Quadrupolar Strain Fields forming a Shear Band in Metallic Glasses

Contact Info

Product

Resources

About