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

2019 ◽  
Vol 9 (1) ◽  
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.

scholarly journals Non-trivial avalanches triggered by shear banding in compression of metallic glass foams

2020 ◽  
Vol 476 (2240) ◽  
pp. 20200186
Author(s):  
H. Lin ◽  
C. lu ◽  
H. Y. Wang ◽  
L. H. Dai
Keyword(s):  
Metallic Glass ◽  
Scaling Laws ◽  
Waiting Times ◽  
Shear Banding ◽  
Shear Bands ◽  
Mean Field ◽  
Structural Disorder ◽  
Aftershock Sequence ◽  
Atomic Scale ◽  
Characteristic Time Scale

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.

A survey of instrumented indentation studies on metallic glasses

2004 ◽  
Vol 19 (1) ◽  
pp. 46-57 ◽  
Author(s):  
C.A. Schuh ◽  
T.G. Nieh
Keyword(s):  
Metallic Glasses ◽  
Structural Changes ◽  
Shear Banding ◽  
Depth Sensing ◽  
Future Directions ◽  
Fundamental Physics ◽  
New Approach ◽  
The Past ◽  
Rate Dependent

The development of instrumented nanoindentation equipment has occurred concurrently with the discovery of many new families of bulk metallic glass during the past decade. While indentation testing has long been used to assess the mechanical properties of metallic glasses, depth-sensing capabilities offer a new approach to study the fundamental physics behind glass deformation. This article is a succinct review of the research to date on the indentation of metallic glasses. In addition to standard hardness measurements, the onset of plasticity in metallic glasses is reviewed as well as the role of shear banding in indentation, structural changes beneath the indenter, and rate-dependent effects measured by nanoindentation. The article concludes with perspectives about the future directions for nanocontact studies on metallic glasses.

scholarly journals Dilatancy induced ductile–brittle transition of shear band in metallic glasses

2018 ◽  
Vol 474 (2212) ◽  
pp. 20170836 ◽  
Author(s):  
F. Zeng ◽  
M. Q. Jiang ◽  
L. H. Dai
Keyword(s):  
Shear Band ◽  
Metallic Glasses ◽  
Shear Failure ◽  
Scaling Law ◽  
Shear Banding ◽  
Structural Evolution ◽  
Atomic Scale ◽  
Serrated Flow ◽  
Brittle Transition ◽  
Evolution Dynamics

Dilatancy-generated structural disordering, an inherent feature of metallic glasses (MGs), has been widely accepted as the physical mechanism for the primary origin and structural evolution of shear banding, as well as the resultant shear failure. However, it remains a great challenge to determine, to what degree of dilatation, a shear banding will evolve into a runaway shear failure. In this work, using in situ acoustic emission monitoring, we probe the dilatancy evolution at the different stages of individual shear band in MGs that underwent severely plastic deformation by the controlled cutting technology. A scaling law is revealed that the dilatancy in a shear band is linearly related to its evolution degree. A transition from ductile-to-brittle shear bands is observed, where the formers dominate stable serrated flow, and the latter lead to a runaway instability (catastrophe failure) of serrated flow. To uncover the underlying mechanics, we develop a theoretical model of shear-band evolution dynamics taking into account an atomic-scale deformation process. Our theoretical results agree with the experimental observations, and demonstrate that the atomic-scale volume expansion arises from an intrinsic shear-band evolution dynamics. Importantly, the onset of the ductile–brittle transition of shear banding is controlled by a critical dilatation.

scholarly journals Strain rate dependence of plastic flow in Ce-based bulk metallic glass during nanoindentation

2007 ◽  
Vol 22 (2) ◽  
pp. 258-263 ◽  
Author(s):  
B.C. Wei ◽  
L.C. Zhang ◽  
T.H. Zhang ◽  
D.M. Xing ◽  
J. Das ◽  
...  
Keyword(s):  
Plastic Deformation ◽  
Metallic Glass ◽  
Strain Rate ◽  
Bulk Metallic Glass ◽  
Loading Rate ◽  
Shear Banding ◽  
Rate Dependence ◽  
Strain Rate Dependence ◽  
Serrated Flow ◽  
Rate Dependent

The strain rate dependence of plastic deformation of Ce60Al15Cu10Ni15 bulk metallic glass was studied by nanoindentation. Even though the ratio of room temperature to the glass transition temperature was very high (0.72) for this alloy, the plastic deformation was dominated by shear banding under nanoindentation. The alloy exhibited a critical loading rate dependent serrated flow feature. That is, with increasing loading rate, the alloy exhibited a transition from less prominent serrated flow to pronounced serrated flow during continuous loading but from serrated to smoother flow during stepped loading.

scholarly journals Probe Embryonic Damage Evolution in Bulk Metallic Glasses under Plate-impact Loading

2018 ◽  
Vol 183 ◽  
pp. 03013
Author(s):  
Zhong Ling ◽  
Xin Huang ◽  
Lanhong Dai
Keyword(s):  
Metallic Glass ◽  
Metallic Glasses ◽  
Volume Content ◽  
Impact Loading ◽  
Damage Evolution ◽  
Ductile Damage ◽  
Plate Impact ◽  
Shear Transformation ◽  
Stress Environment ◽  
Shear Transformation Zones

Microdamage in very short stress durations of spallation process in Zr-based bulk metallic glass (Zr-BMG) samples were captured by a specially designed plate impact technique. With stress durations vary, microdamage “frozen” in Zr-BMG samples exhibited different damage levels. Based on the morphology and stress environment of the microdamage, a compound microdamage evolution mode is applied to characterize the spallation evolution in Zr-BMGs. Especially the spallation in BMGs originates from cavitation instabilities in the weak regions with higher free volume content, which results in formation of ductile damage zones. The activation of shear transformation zones (STZs) or tension transformation zones (TTZs) between these ductile damage zones finally leads to detached spallation.

scholarly journals The Evolution of Micromechanical Properties for Zr-Based Metallic Glass Induced by Laser Shock Peening

2021 ◽  
Vol 8 ◽  
Author(s):  
Yansen Li ◽  
Zhitao Wang ◽  
Yanpeng Wei ◽  
Tianyu Chen ◽  
Chunfeng Zhang ◽  
...  
Keyword(s):  
Plastic Deformation ◽  
Metallic Glass ◽  
Metallic Glasses ◽  
Laser Shock Peening ◽  
Laser Shock ◽  
Micromechanical Properties ◽  
Shock Region ◽  
Deformation Ability ◽  
Shock Peening ◽  
The Impact

The micromechanical properties of Zr-based metallic glass (MG) induced by laser shock peening (LSP) were studied through the use of nanoindentation. The serrations in representative load-displacement (P-h) curves exhibited a transformation from stairstep-like to ripple-shaped from untreated zone to shock region, which implied an increase in plastic deformation ability of material after LSP. Significant hardening was also observed in the impact zone, which can be attributed to the effect of compressive residual stress. Both increase in hardness and plastic deformation ability in shock region indicate the excellent effect of LSP on the micromechanical properties of investigated Zr-based MG, which provide a new way to study the deformation mechanism in metallic glasses and a further understanding of plasticization.

Effect of frame stiffness on the deformation behavior of bulk metallic glass

2010 ◽  
Vol 25 (10) ◽  
pp. 1958-1962 ◽  
Author(s):  
Z. Han ◽  
Y. Li ◽  
H.J. Gao
Keyword(s):  
Metallic Glass ◽  
Bulk Metallic Glass ◽  
Metallic Glasses ◽  
Deformation Behavior ◽  
Shear Banding ◽  
Bulk Metallic Glasses ◽  
Designed Experiments ◽  
Machine Stiffness ◽  
The Stability ◽  
Frame Stiffness

It has been shown that the stability of shear banding and plasticity of bulk metallic glasses (BMGs) can be strongly influenced by the machine stiffness. Here, we demonstrated that the practice of adding a frame parallel to the sample is quantitatively equivalent to increasing the machine stiffness by the frame stiffness. A series of carefully designed experiments were conducted to verify such an effect, showing controllably enhanced plasticity of BMG samples.

scholarly journals Fast surface dynamics enabled cold joining of metallic glasses

2019 ◽  
Vol 5 (11) ◽  
pp. eaax7256 ◽  
Author(s):  
Jiang Ma ◽  
Can Yang ◽  
Xiaodi Liu ◽  
Baoshuang Shang ◽  
Quanfeng He ◽  
...  
Keyword(s):  
Metallic Glass ◽  
Metallic Glasses ◽  
Materials Science ◽  
Atomic Scale ◽  
Glass Transition Point ◽  
Grand Challenge ◽  
Surface Dynamics ◽  
Science And Engineering ◽  
Glass Composites ◽  
Materials Science And Engineering

Design of bulk metallic glasses (BMGs) with excellent properties has been a long-sought goal in materials science and engineering. The grand challenge has been scaling up the size and improving the properties of metallic glasses of technological importance. In this work, we demonstrate a facile, flexible route to synthesize BMGs and metallic glass-glass composites out of metallic-glass ribbons. By fully activating atomic-scale stress relaxation within an ultrathin surface layer under ultrasonic vibrations, we accelerate the formation of atomic bonding between ribbons at a temperature far below the glass transition point. In principle, our approach overcomes the size and compositional limitations facing traditional methods, leading to the rapid bonding of metallic glasses of distinct physical properties without causing crystallization. The outcome of our current research opens up a window not only to synthesize BMGs of extended compositions, but also toward the discovery of multifunctional glass-glass composites, which have never been reported before.

Rate-dependent shear banding and fracture behavior in a ductile bulk metallic glass

2018 ◽  
Vol 730 ◽  
pp. 270-279 ◽  
Author(s):  
Ding Zhou ◽  
Bingjin Li ◽  
Shuangyin Zhang ◽  
Bing Hou ◽  
Yulong Li
Keyword(s):  
Metallic Glass ◽  
Bulk Metallic Glass ◽  
Fracture Behavior ◽  
Shear Banding ◽  
Rate Dependent
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