scholarly journals In situ transmission electron microscopy studies of shear bands in a bulk metallic glass based composite

2001 ◽  
Vol 16 (9) ◽  
pp. 2513-2518 ◽  
Author(s):  
E. Pekarskaya ◽  
C. P. Kim ◽  
W. L. Johnson
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Metallic Glass ◽  
Bulk Metallic Glass ◽  
Crystalline Phase ◽  
Shear Bands ◽  
Quantitative Parameters ◽  
Transmission Electron ◽  
Narrow Bands

In situ straining transmission electron microscopy (TEM) experiments were performed to study the propagation of the shear bands in the Zr56.3Ti13.8Cu6.9Ni5.6Nb5.0Be12.5 bulk metallic glass based composite. Contrast in TEM images produced by shear bands in metallic glass and quantitative parameters of the shear bands were analyzed. It was determined that, at a large amount of shear in the glass, the localization of deformation occurs in the crystalline phase, where formation of dislocations within the narrow bands are observed.

Structure of shear bands in Pd40Ni40P20 bulk metallic glass

2009 ◽  
Vol 24 (1) ◽  
pp. 1-9 ◽  
Author(s):  
Y.M. Chen ◽  
T. Ohkubo ◽  
T. Mukai ◽  
K. Hono
Keyword(s):  
Electron Microscopy ◽  
Metallic Glass ◽  
Bulk Metallic Glass ◽  
Short Range ◽  
Short Range Order ◽  
Shear Bands ◽  
Distribution Functions ◽  
Uniform Thickness ◽  
Transmission Electron ◽  
Pair Distribution Functions

The atomic structure of shear bands in Pd40Ni40P20 bulk metallic glass has been compared to an undeformed matrix phase using pair distribution functions (PDFs) derived from energy filtered nanobeam electron diffraction. Shear bands do not show any characteristic contrast in transmission electron microscopy (TEM) images when specimens are prepared with uniform thickness. PDFs from a shear band exhibit a slight decrease in the first peak, indicating a slight difference in packing density and short range order compared to the undeformed matrix.

Comment on “Homogeneity of Zr64.13Cu15.75Ni10.12Al10 bulk metallic glass,” by L-Y. Chen, Y-W. Zeng, Q-P. Cao, B-J. Park, Y-M. Chen, K. Hono, U. Vainio, Z-L. Zhang, U. Kaiser, X-D. Wang, and J-Z. Jiang [J. Mater. Res. 24, 3116 (2009)]

2010 ◽  
Vol 25 (3) ◽  
pp. 598-601 ◽  
Author(s):  
Yanhui Liu ◽  
Wei H. Wang
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Metallic Glass ◽  
Bulk Metallic Glass ◽  
Structural Heterogeneity ◽  
Microstructural Observation ◽  
X Ray ◽  
X Ray Scattering ◽  
Transmission Electron ◽  
Structural Heterogeneities

In a recent work, Chen et al. [L-Y. Chen et al., J. Mater. Res.24, 3116 (2009)] presented microstructural observation on a plastic Zr64.13Cu15.75Ni10.12Al10 bulk metallic glass (BMG) reported in Liu et al. [Y.H. Liu et al., Science315, 1385 (2007)] by using transmission electron microscopy (TEM) and anomalous small-angle x-ray scattering experiments. Based on their observation, they draw a conclusion that there are no micrometer-sized or nanometer-sized structural heterogeneities in the BMG, and the large plasticity of the BMG cannot be ascribed to the structural heterogeneities. In this comment, we show that their assessment and analysis of their observation are problematic, and it is not evident and precise to use their observation to claim that the BMG is homogeneous and the structural heterogeneity in the glass is an artifact.

Initiation and evolution of shear bands in bulk metallic glass under tension—An in situ scanning electron microscopy observation

2009 ◽  
Vol 24 (9) ◽  
pp. 2924-2930 ◽  
Author(s):  
Qingping Cao ◽  
Feng Xu ◽  
Jingwei Liu ◽  
Lianyi Chen ◽  
Xiaodong Wang ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Yield Strength ◽  
Shear Band ◽  
Metallic Glass ◽  
Bulk Metallic Glass ◽  
Shear Bands ◽  
Maximum Pressure ◽  
Scanning Electron

The initiation and evolution of shear bands in Zr64.13Cu15.75Ni10.12Al10 bulk metallic glass tensile samples has been investigated in situ by scanning electron microscopy. The initial shear band originates from the highest stressed area, and does not propagate during further tension, which is attributed to the weakening of the stress field in front of the shear band tip, possibly caused by atomic rearrangement and local temperature rise. As a result, multiple shear bands occur in sequence with gradually increased length and offset. This result is due to the fact that the stress in front of the tip of the initial shear band does not concentrate again during further tension above the shear yield strength. Numerical analysis was carried out to investigate the stress distribution under tension, suggesting that the maximum pressure-dependent shear stress criterion overestimates the yield strength, while the shear plane criterion describes the conditions for the formation of shear bands well.

Epitaxy and texture analysis of Bi-Sr-Ca-Cu-O thin films on (100) MgO using Transmission Electron Microscopy

1990 ◽  
Vol 48 (4) ◽  
pp. 68-69
Author(s):  
J. T. Sizemore ◽  
D. G. Schlom ◽  
Z. J. Chen ◽  
J. N. Eckstein ◽  
I. Bozovic ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Thin Films ◽  
Transmission Electron Microscopy ◽  
Critical Currents ◽  
Unit Cell ◽  
X Ray Diffraction ◽  
Cell Axis ◽  
Transmission Electron ◽  
Synthesis Procedure

Investigators observe large critical currents for superconducting thin films deposited epitaxially on single crystal substrates. The orientation of these films is often characterized by specifying the unit cell axis that is perpendicular to the substrate. This omits specifying the orientation of the other unit cell axes and grain boundary angles between grains of the thin film. Misorientation between grains of YBa2Cu3O7−δ decreases the critical current, even in those films that are c axis oriented. We presume that these results are similar for bismuth based superconductors and report the epitaxial orientations and textures observed in such films.Thin films of nominally Bi2Sr2CaCu2Ox were deposited on MgO using molecular beam epitaxy (MBE). These films were in situ grown (during growth oxygen was incorporated and the films were not oxygen post-annealed) and shuttering was used to encourage c axis growth. Other papers report the details of the synthesis procedure. The films were characterized using x-ray diffraction (XRD) and transmission electron microscopy (TEM).

Transmission Electron Microscopy of Epitaxial silicides grown by ultra high vacuum deposition

1989 ◽  
Vol 47 ◽  
pp. 462-463
Author(s):  
D. Loretto ◽  
J. M. Gibson ◽  
S. M. Yalisove
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Electron Diffraction ◽  
High Vacuum ◽  
High Energy ◽  
Energy Electron ◽  
Ultra High Vacuum ◽  
Ex Situ ◽  
Transmission Electron

The silicides CoSi2 and NiSi2 are both metallic with the fee flourite structure and lattice constants which are close to silicon (1.2% and 0.6% smaller at room temperature respectively) Consequently epitaxial cobalt and nickel disilicide can be grown on silicon. If these layers are formed by ultra high vacuum (UHV) deposition (also known as molecular beam epitaxy or MBE) their thickness can be controlled to within a few monolayers. Such ultrathin metal/silicon systems have many potential applications: for example electronic devices based on ballistic transport. They also provide a model system to study the properties of heterointerfaces. In this work we will discuss results obtained using in situ and ex situ transmission electron microscopy (TEM).In situ TEM is suited to the study of MBE growth for several reasons. It offers high spatial resolution and the ability to penetrate many monolayers of material. This is in contrast to the techniques which are usually employed for in situ measurements in MBE, for example low energy electron diffraction (LEED) and reflection high energy electron diffraction (RHEED), which are both sensitive to only a few monolayers at the surface.

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