Revelation of the effect of structural heterogeneity on microplasticity in bulk metallic-glasses

2010 ◽  
Vol 25 (3) ◽  
pp. 563-575 ◽  
Author(s):  
Yong Yang ◽  
Jianchao Ye ◽  
Jian Lu ◽  
Qing Wang ◽  
Peter K. Liaw
Keyword(s):  
Metallic Glasses ◽  
Focused Ion Beam ◽  
Ion Beam ◽  
Shear Banding ◽  
Shear Bands ◽  
Bulk Metallic Glasses ◽  
Three Dimensional ◽  
Structural Heterogeneity ◽  
Submicron Scale ◽  
Three Dimensional Finite Element

In this article, the shear-banding behavior in bulk metallic-glasses (BMGs) is studied using a focused ion beam (FIB)-based nanoindentation method, which involves cylindrical nanoindentation of a FIB-milled BMG microlamella and is capable of revealing the subsurface shear-band patterns down to the submicron scale. The results of the current study on a Zr-based BMG clearly show that short shear bands, with the lengths of a few hundred nanometers, could be severely kinked before growing into a longer one, which implies that structural heterogeneity plays an important role in the microplasticity of BMGs. Furthermore, through the three-dimensional finite-element simulation combined with the theoretical calculation based on the Mohr–Coulomb law, it is found that the yield strengths exhibit a large scatter as a consequence of the structural heterogeneity when microplasticity occurs in the Zr-based BMG, which is consistent with our recent findings obtained from the microcompression experiments.

Effects of sample geometry on deformation modes of bulk metallic glasses at the nano/micrometer scale

2009 ◽  
Vol 24 (11) ◽  
pp. 3465-3468 ◽  
Author(s):  
Jianchao Ye ◽  
Jian Lu ◽  
Yong Yang ◽  
Peter K. Liaw
Keyword(s):  
Metallic Glasses ◽  
Shear Banding ◽  
Shear Bands ◽  
Bulk Metallic Glasses ◽  
Deformation Mode ◽  
Homogeneous Deformation ◽  
Sample Geometry ◽  
Submicron Scale ◽  
Proper Modification ◽  
Micrometer Scale

Intense debates have been prompted concerning whether homogeneous deformation can be achieved in bulk metallic glasses at room temperature through the suppression of shear bands at the submicron scale. In this short communication, we demonstrate that multiple shear banding can be successfully attained via a proper modification of the microsample geometry, resulting in the appearance of a homogeneous deformation mode at the submicron scale. However, the apparent deformation homogeneity in our microcompression experiment is a manifestation of the sample geometry effect on the propagation rather than nucleation of shear bands.

A finite element model to study the effect of porosity location on the elastic modulus of a cantilever beam

2019 ◽  
Vol 43 (4) ◽  
pp. 443-453
Author(s):  
Stephen M. Handrigan ◽  
Sam Nakhla
Keyword(s):  
Finite Element ◽  
Elastic Modulus ◽  
Focused Ion Beam ◽  
Mechanical Response ◽  
Ion Beam ◽  
Three Dimensional ◽  
Beam Theory ◽  
Element Model ◽  
Fe Model ◽  
Three Dimensional Finite Element

An investigation to determine the effect of porosity concentration and location on elastic modulus is performed. Due to advancements in testing methods, the manufacturing and testing of microbeams to obtain mechanical response is possible through the use of focused ion beam technology. Meanwhile, rigorous analysis is required to enable accurate extraction of the elastic modulus from test data. First, a one-dimensional investigation with beam theory, Euler–Bernoulli and Timoshenko, was performed to estimate the modulus based on load-deflection curve. Second, a three-dimensional finite element (FE) model in Abaqus was developed to identify the effect of porosity concentration. Furthermore, the current work provided an accurate procedure to enable accurate extraction of the elastic modulus from load-deflection data. The use of macromodels such as beam theory and three-dimensional FE model enabled enhanced understanding of the effect of porosity on modulus.

In-situ TEM investigation of deformation behavior of metallic glass pillars

2009 ◽  
Vol 1185 ◽  
Author(s):  
Changqiang Chen ◽  
Yutao Pei ◽  
Jeff De Hosson
Keyword(s):  
Metallic Glass ◽  
Focused Ion Beam ◽  
Axial Stress ◽  
Ion Beam ◽  
Shear Banding ◽  
Shear Bands ◽  
Deformation Mode ◽  
In Situ Tem ◽  
Compression Tests

AbstractWe show results of in situ TEM (Transmission electron microscope) quantitative investigations on the compression behaviors of amorphous micropillars fabricated by focused ion beam from Cu47Ti33Zr11Ni6Sn2Si1 metallic glass (MG) ribbon. Pillars with well defined gauge sections and tip diameter ranging from 100 nm to 640 nm are studied. Quantitative compression tests were performed by a recently developed Picoindenter TEM holder, with the evolution of individual shear bands monitored in real time in TEM. It is found that the deformation of the MG pillars at the present size domain is still dominated by discrete shear banding as demonstrated by intermittent events in the load-displacement curves. However, the frequency, amplitude and distribution of these shear banding events are clearly size dependent at submicrometer scale, leading to an apparently transition in deformation mode from highly localized inhomogeneous deformation to less localized and more distributed deformation with decreasing pillars diameter. Deformation of a 105 nm diameter pillar having rounded tips is characterized with fully homogeneous bulge at the initial stage of deformation, indicating prompting effect of multi-axial stress state on transition to fully homogeneous deformation.

scholarly journals Unraveling submicron-scale mechanical heterogeneity by three-dimensional X-ray microdiffraction

2017 ◽  
Vol 115 (3) ◽  
pp. 483-488 ◽  
Author(s):  
Runguang Li ◽  
Qingge Xie ◽  
Yan-Dong Wang ◽  
Wenjun Liu ◽  
Mingguang Wang ◽  
...  
Keyword(s):  
Lattice Strain ◽  
Shear Banding ◽  
Shear Bands ◽  
Three Dimensional ◽  
Bulk Materials ◽  
Mechanical Heterogeneity ◽  
Strain Gradients ◽  
X Ray ◽  
Submicron Scale ◽  
Submicron Resolution

Shear banding is a ubiquitous phenomenon of severe plastic deformation, and damage accumulation in shear bands often results in the catastrophic failure of a material. Despite extensive studies, the microscopic mechanisms of strain localization and deformation damage in shear bands remain elusive due to their spatial−temporal complexities embedded in bulk materials. Here we conducted synchrotron-based X-ray microdiffraction (μXRD) experiments to map out the 3D lattice strain field with a submicron resolution around fatigue shear bands in a stainless steel. Both in situ and postmortem μXRD results revealed large lattice strain gradients at intersections of the primary and secondary shear bands. Such strain gradients resulted in severe mechanical heterogeneities across the fatigue shear bands, leading to reduced fatigue limits in the high-cycle regime. The ability to spatially quantify the localized strain gradients with submicron resolution through μXRD opens opportunities for understanding the microscopic mechanisms of damage and failure in bulk materials.

Experimental Study on the Effect of Normal Stress on the Shear Banding in a Zr-Based Bulk Metallic Glasses

2010 ◽  
Vol 146-147 ◽  
pp. 424-428
Author(s):  
Long Fei Liu ◽  
Jing Hu ◽  
Hui Qiang Li ◽  
Guang Ye Zhang
Keyword(s):  
Experimental Study ◽  
Shear Stress ◽  
Normal Stress ◽  
Metallic Glasses ◽  
Shear Banding ◽  
Shear Bands ◽  
Bulk Metallic Glasses ◽  
Numerical Density ◽  
Plastic Displacement ◽  
Inclined Angle

A special fixture, which can control the ratio(λ) of normal stress/shear stress, was used to study the effect of normal stress on the shear banding behaviors in a Zr-based bulk metallic glasses in the present paper. The experimental results demonstrated that the plastic displacement increased with increasing of λ. Observations of shear bands pattern on the sample surfaces indicated that normal stress have significant impact on the inclined angle, numerical density and length of shear bands. In addition, normal stress is the major factor of inducing multiple shear bands with intersecting, branching and slipping. Based on the observations, the mechanism of plasticity enhancement due to the increasing of normal stress was explored.

scholarly journals CHARACTERIZATION OF SHEAR BANDS IN TWO BULK METALLIC GLASSES WITH DIFFERENT INHERENT PLASTICITY

2009 ◽  
Vol 23 (06n07) ◽  
pp. 1217-1222 ◽  
Author(s):  
JIANSHENG GU ◽  
LEI LI ◽  
TAIHUA ZHANG ◽  
PENG JIANG ◽  
BINGCHEN WEI ◽  
...  
Keyword(s):  
Shear Band ◽  
Metallic Glasses ◽  
Shear Banding ◽  
Shear Bands ◽  
Bulk Metallic Glasses ◽  
Similar Chemical ◽  
Significant Difference ◽  
Band Spacing ◽  
Plastic Deformation Region

Shear banding characterization of Zr 64.13 Cu 15.75 Ni 10.12 Al 10 and Zr 65 Cu 15 Ni 10 Al 10 bulk metallic glasses (BMGs) with significant difference in inherent plasticity and quite similar chemical composition was studied by depth sensitive macroindentaion tests with conical indenter. Well-developed shear band pattern can be found for both BMGs after indentation. Distinct difference in the shear band spacing, scale of plastic deformation region and the shear band branching in the two BMGs account for the different plasticity.

Observations of nanoindents via cross-sectional transmission electron microscopy: a survey of deformation mechanisms

2005 ◽  
Vol 461 (2060) ◽  
pp. 2521-2543 ◽  
Author(s):  
S.J Lloyd ◽  
A Castellero ◽  
F Giuliani ◽  
Y Long ◽  
K.K McLaughlin ◽  
...  
Keyword(s):  
Cross Sections ◽  
Focused Ion Beam ◽  
Ion Beam ◽  
Deformation Behaviour ◽  
Shear Bands ◽  
Three Dimensional ◽  
Deformation Mechanisms ◽  
Lattice Rotation ◽  
Cross Sectional ◽  
Transmission Electron

Examination of cross-sections of nanoindents with the transmission electron microscope has recently become feasible owing to the development of focused ion beam milling of site-specific electron transparent foils. Here, we discuss the development of this technique for the examination of nanoindents and survey the deformation behaviour in a range of single crystal materials with differing resistances to dislocation flow. The principal deformation modes we discuss, in addition to dislocation flow, are phase transformation (silicon and germanium), twinning (gallium arsenide and germanium at 400 °C), lattice rotations (spinel), shear (spinel), lattice rotations (copper) and lattice rotations and densification (TiN/NbN multilayers). The magnitude of the lattice rotation, about the normal to the foil, was measured at different positions under the indents. Indents in a partially recrystallized metallic glass Mg 66 Ni 20 Nd 14 were also examined. In this case a low-density porous region was formed at the indent tip and evidence of shear bands was also found. Further understanding of indentation deformation will be possible with three-dimensional characterization coupled with modelling which takes account of the variety of competing deformation mechanisms that can occur in addition to dislocation glide. Mapping the lattice rotations will be a particularly useful way to evaluate models of the deformation process.

3D Observation of Elemental Distribution of Si-Device using a Dedicated FIB/STEM System

2005 ◽  
Author(s):  
T. Yaguchi ◽  
M. Konno ◽  
T. Kamino ◽  
M. Ogasawara ◽  
K. Kaji ◽  
...  
Keyword(s):  
Focused Ion Beam ◽  
Ion Beam ◽  
Three Dimensional ◽  
Elemental Distribution ◽  
Multivariate Statistical ◽  
X Ray ◽  
Sample Rotation ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Elemental Maps

Abstract A technique for preparation of a pillar shaped sample and its multi-directional observation of the sample using a focused ion beam (FIB) / scanning transmission electron microscopy (STEM) system has been developed. The system employs an FIB/STEM compatible sample rotation holder with a specially designed rotation mechanism, which allows the sample to be rotated 360 degrees [1-3]. This technique was used for the three dimensional (3D) elemental mapping of a contact plug of a Si device in 90 nm technology. A specimen containing a contact plug was shaped to a pillar sample with a cross section of 200 nm x 200 nm and a 5 um length. Elemental analysis was performed with a 200 kV HD-2300 STEM equipped with the EDAX genesis Energy dispersive X-ray spectroscopy (EDX) system. Spectrum imaging combined with multivariate statistical analysis (MSA) [4, 5] was used to enhance the weak X-ray signals of the doped area, which contain a low concentration of As-K. The distributions of elements, especially the dopant As, were successfully enhanced by MSA. The elemental maps were .. reconstructed from the maps.

scholarly journals Investigation of the selective color-changing mechanism of Dynastes tityus beetle (Coleoptera: Scarabaeidae)

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Jiyu Sun ◽  
Wei Wu ◽  
Limei Tian ◽  
Wei Li ◽  
Fang Zhang ◽  
...  
Keyword(s):  
Focused Ion Beam ◽  
Color Change ◽  
Incidence Angle ◽  
Ion Beam ◽  
Three Dimensional ◽  
Water Infiltration ◽  
Photonic Materials ◽  
Local Color ◽  
Water Contact ◽  
Color Changes

AbstractNot only does the Dynastes tityus beetle display a reversible color change controlled by differences in humidity, but also, the elytron scale can change color from yellow-green to deep-brown in specified shapes. The results obtained by focused ion beam-scanning electron microscopy (FIB-SEM), show that the epicuticle (EPI) is a permeable layer, and the exocuticle (EXO) is a three-dimensional photonic crystal. To investigate the mechanism of the reversible color change, experiments were conducted to determine the water contact angle, surface chemical composition, and optical reflectance, and the reflective spectrum was simulated. The water on the surface began to permeate into the elytron via the surface elemental composition and channels in the EPI. A structural unit (SU) in the EXO allows local color changes in varied shapes. The reflectance of both yellow-green and deep-brown elytra increases as the incidence angle increases from 0° to 60°. The microstructure and changes in the refractive index are the main factors that influence the process of reversible color change. According to the simulation, the lower reflectance causing the color change to deep-brown results from water infiltration, which increases light absorption. Meanwhile, the waxy layer has no effect on the reflection of light. This study lays the foundation to manufacture engineered photonic materials that undergo controllable changes in iridescent color.

scholarly journals Protocol for preparation of heterogeneous biological samples for 3D electron microscopy: a case study for insects

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Alexey A. Polilov ◽  
Anastasia A. Makarova ◽  
Song Pang ◽  
C. Shan Xu ◽  
Harald Hess
Keyword(s):  
Electron Microscopy ◽  
Biological Samples ◽  
Focused Ion Beam ◽  
Ion Beam ◽  
Three Dimensional ◽  
Entire Volume ◽  
Simple Protocol ◽  
3D Electron Microscopy ◽  
3D Em

AbstractModern morphological and structural studies are coming to a new level by incorporating the latest methods of three-dimensional electron microscopy (3D-EM). One of the key problems for the wide usage of these methods is posed by difficulties with sample preparation, since the methods work poorly with heterogeneous (consisting of tissues different in structure and in chemical composition) samples and require expensive equipment and usually much time. We have developed a simple protocol allows preparing heterogeneous biological samples suitable for 3D-EM in a laboratory that has a standard supply of equipment and reagents for electron microscopy. This protocol, combined with focused ion-beam scanning electron microscopy, makes it possible to study 3D ultrastructure of complex biological samples, e.g., whole insect heads, over their entire volume at the cellular and subcellular levels. The protocol provides new opportunities for many areas of study, including connectomics.

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