Atomic scale calculation of the free volume in Zr2Ni metallic glass

Ductile metallic glass foams (DMGFs) are a new type of structural material with a perfect combination of high strength and toughness. Owing to their disordered atomic-scale microstructures and randomly distributed macroscopic voids, the compressive deformation of DMGFs proceeds through multiple nanoscale shear bands accompanied by local fracture of cellular structures, which induces avalanche-like intermittences in stress–strain curves. In this paper, we present a statistical analysis, including distributions of avalanche size, energy dissipation, waiting times and aftershock sequence, on such a complex dynamic process, which is dominated by shear banding. After eliminating the influence of structural disorder, we demonstrate that, in contrast to the mean-field results of their brittle counterparts, scaling laws in DMGFs are characterized by different exponents. It is shown that the occurrence of non-trivial scaling behaviours is attributed to the localized plastic yielding, which effectively prevents the system from building up a long-range correlation. This accounts for the high structural stability and energy absorption performance of DMGFs. Furthermore, our results suggest that such shear banding dynamics introduce an additional characteristic time scale, which leads to a universal gamma distribution of waiting times.

Download Full-text

Atomic-scale viscoplasticity mechanisms revealed in high ductility metallic glass films

Scientific Reports ◽

10.1038/s41598-019-49910-7 ◽

2019 ◽

Vol 9 (1) ◽

Cited By ~ 3

Author(s):

Hosni Idrissi ◽

Matteo Ghidelli ◽

Armand Béché ◽

Stuart Turner ◽

Sébastien Gravier ◽

...

Keyword(s):

Metallic Glass ◽

Metallic Glasses ◽

Shear Banding ◽

Atomic Scale ◽

Microscopy Imaging ◽

Rate Dependent ◽

Imaging And Spectroscopy ◽

Shear Transformation Zones ◽

The Impact ◽

Glass Films

Abstract The fundamental plasticity mechanisms in thin freestanding Zr65Ni35 metallic glass films are investigated in order to unravel the origin of an outstanding strength/ductility balance. The deformation process is homogenous until fracture with no evidence of catastrophic shear banding. The creep/relaxation behaviour of the films was characterized by on-chip tensile testing, revealing an activation volume in the range 100–200 Å3. Advanced high-resolution transmission electron microscopy imaging and spectroscopy exhibit a very fine glassy nanostructure with well-defined dense Ni-rich clusters embedded in Zr-rich clusters of lower atomic density and a ~2–3 nm characteristic length scale. Nanobeam electron diffraction analysis reveals that the accumulation of plastic deformation at room-temperature correlates with monotonously increasing disruption of the local atomic order. These results provide experimental evidences of the dynamics of shear transformation zones activation in metallic glasses. The impact of the nanoscale structural heterogeneities on the mechanical properties including the rate dependent behaviour is discussed, shedding new light on the governing plasticity mechanisms in metallic glasses with initially heterogeneous atomic arrangement.

Download Full-text

Atomic-scale structural evolution in selective laser melting of Cu50Zr50 metallic glass

Computational Materials Science ◽

10.1016/j.commatsci.2018.03.072 ◽

2018 ◽

Vol 150 ◽

pp. 62-69 ◽

Cited By ~ 8

Author(s):

Yue Zhang ◽

Haishun Liu ◽

Jinyong Mo ◽

Mingzi Wang ◽

Zhe Chen ◽

...

Keyword(s):

Metallic Glass ◽

Selective Laser Melting ◽

Structural Evolution ◽

Atomic Scale ◽

Laser Melting

Download Full-text

Numerical Study on the Fatigue Limit of Metallic Glasses under Cyclic Tension-Compression Loading

Materials ◽

10.3390/ma13071732 ◽

2020 ◽

Vol 13 (7) ◽

pp. 1732

Author(s):

Jinfeng Yan ◽

Wenjun Meng ◽

Zhi Chen ◽

Hong Guo ◽

Xianguo Yan

Keyword(s):

Fatigue Life ◽

Metallic Glass ◽

Fatigue Limit ◽

Free Volume ◽

Strain Amplitude ◽

Numerical Study ◽

Hydrostatic Stress ◽

Shear Banding ◽

Engineering Application ◽

Free Volume Theory

Numerical study was performed to determine the fatigue limit of metallic glass under tension-compression cyclic loading. A revised free-volume theory which considers the hydrostatic stress was utilized to make the predictions. Systematical simulations showed that a higher strain amplitude is prone to making the sample completely damaged earlier. However, lower strain fluctuations could result in a longer fatigue life. Shear banding evolution history described by free-volume localization could reasonably explain the mechanical responses of different samples. In addition, compressive loading could give rise to a higher stress than that under tensile loading because of hydrostatic stress contribution. In the end, a correlation between fatigue life and applied strain amplitude was plotted which could supply a guidance for designing the engineering application of metallic glass under periodic loading.

Download Full-text

Influence of size-dependent free volume variation and distribution on the thermoplastic flow behavior of Zr-based bulk metallic glass

Journal of Alloys and Compounds ◽

10.1016/j.jallcom.2018.12.327 ◽

2019 ◽

Vol 783 ◽

pp. 272-278 ◽

Cited By ~ 1

Author(s):

Lei Deng ◽

Di Yao ◽

Peng Zhou ◽

Xinyun Wang ◽

Pan Gong

Keyword(s):

Metallic Glass ◽

Bulk Metallic Glass ◽

Free Volume ◽

Flow Behavior ◽

Size Dependent ◽

Volume Variation

Download Full-text

Effect of Structure Relaxation on the Plastic Deformation Behaviour in a Zr-Based BMG under Indenter

Materials Science Forum ◽

10.4028/www.scientific.net/msf.618-619.437 ◽

2009 ◽

Vol 618-619 ◽

pp. 437-441

Author(s):

Hao Wen Xie ◽

Peter D. Hodgson ◽

Cui E Wen

Keyword(s):

Plastic Deformation ◽

Shear Band ◽

Metallic Glass ◽

Bulk Metallic Glass ◽

Free Volume ◽

Cast Alloy ◽

Deformation Behaviour ◽

Shear Bands ◽

Structure Relaxation ◽

Effect Of Structure

Vickers and nano indentations were performed on a structurally relaxed Zr41Ti14Cu12.5Ni10Be22.5 bulk metallic glass (BMG), and the evolution of the shear bands in the relaxed BMG was investigated and compared to that in the as-cast alloy. Results indicate that the plastic deformation in the BMG with structure relaxation is accommodated by the semicircular (primary) and radial (secondary) as well as tertiary shear bands. Quantitatively, the shear band density in the relaxed alloy was much lower than that in the as-cast alloy. The annihilation of free volume caused by the annealing was responsible for the embrittlement of the sample with structure relaxation.

Download Full-text

Fast coalescence of metallic glass nanoparticles

Nature Communications ◽

10.1038/s41467-019-13054-z ◽

2019 ◽

Vol 10 (1) ◽

Cited By ~ 4

Author(s):

Yuan Tian ◽

Wei Jiao ◽

Pan Liu ◽

Shuangxi Song ◽

Zhen Lu ◽

...

Keyword(s):

Metallic Glass ◽

Ostwald Ripening ◽

Kinetic Monte Carlo ◽

High Surface ◽

Chemical Properties ◽

Supercooled Liquid ◽

Atomic Scale ◽

Surface Mobility ◽

Coarsening Kinetics ◽

Amorphous Nanoparticles

AbstractThe coarsening of crystalline nanoparticles, driven by reduction of surface energy, is the main factor behind the degeneration of their physical and chemical properties. The kinetic phenomenon has been well described by various models, such as Ostwald ripening and coalescence. However, the coarsening mechanisms of metallic glass nanoparticles (MGNs) remains largely unknown. Here we report atomic-scale observations on the coarsening kinetics of MGNs at high temperatures by in situ heating high-resolution transmission electron microscopy. The coarsening of the amorphous nanoparticles takes place by fast coalescence which is dominated by facet-free surface diffusion at a lower onset temperature. Atomic-scale observations and kinetic Monte Carlo simulations suggest that the high surface mobility and the structural isotropy of MGNs, originating from the disordered structure and unique supercooled liquid state, promote the fast coalescence of the amorphous nanoparticles at relatively lower temperatures.

Download Full-text

Retraction: Atomic-scale simulation to study the dynamical properties and local structure of Cu–Zr and Ni–Zr metallic glass-forming alloys

Physical Chemistry Chemical Physics ◽

10.1039/c6cp90176j ◽

2016 ◽

Vol 18 (29) ◽

pp. 19976-19976 ◽

Cited By ~ 1

Author(s):

M. H. Yang ◽

Y. Li ◽

J. H. Li ◽

B. X. Liu

Keyword(s):

Metallic Glass ◽

Local Structure ◽

Chem Phys ◽

Atomic Scale ◽

Glass Forming ◽

Dynamical Properties ◽

Phys Chem Chem Phys

Retraction of ‘Atomic-scale simulation to study the dynamical properties and local structure of Cu–Zr and Ni–Zr metallic glass-forming alloys’ by M. H. Yang et al., Phys. Chem. Chem. Phys., 2016, 18, 7169–7183.

Download Full-text