The Evolution of Prior-BCC Grain Boundary Cracking During In-situ Creep Deformation of a Ti-15Al-33Nb(at%) Alloy

2006 ◽  
Vol 980 ◽  
Author(s):  
Christopher J. Cowen ◽  
Carl J. Boehlert
Keyword(s):  
Grain Boundary ◽  
Damage Evolution ◽  
Damage Accumulation ◽  
Vacuum Chamber ◽  
Creep Damage ◽  
Sample Surface ◽  
Tensile Creep ◽  
Backscattered Electron ◽  
Scanning Electron

AbstractIn-situ tensile-creep experiments were performed on a Ti-15Al-33Nb(at%) alloy using a specialized tensile stage placed within the vacuum chamber of a Camscan 44 FE scanning electron microscope (SEM). The creep damage evolution on the sample surface was chronicled through backscattered electron (BSE) imaging as a function of stress, time, and creep displacement at 650°C. The experiments revealed that the prior-BCC grain boundaries were the locus of damage accumulation during creep and significant grain boundary cracking was observed. The grain boundary cracking was verified to occur within the bulk of the material through post-mortem analysis.

In Situ Study of Live Specimens in an Environmental Scanning Electron Microscope

2013 ◽  
Vol 19 (4) ◽  
pp. 914-918 ◽  
Author(s):  
Eva Tihlaříková ◽  
Vilém Neděla ◽  
Makoto Shiojiri
Keyword(s):  
Electron Microscope ◽  
Scanning Electron Microscope ◽  
Water Layer ◽  
Sample Surface ◽  
Primary Electron ◽  
Environmental Scanning Electron Microscope ◽  
Working Environment ◽  
Environmental Scanning ◽  
Scanning Electron

AbstractIn this paper we introduce new methodology for the observation of living biological samples in an environmental scanning electron microscope (ESEM). The methodology is based on an unconventional initiation procedure for ESEM chamber pumping, free from purge–flood cycles, and on the ability to control thermodynamic processes close to the sample. The gradual and gentle change of the working environment from air to water vapor enables the study of not only living samples in dynamic in situ experiments and their manifestation of life (sample walking) but also its experimentally stimulated physiological reactions. Moreover, Monte Carlo simulations of primary electron beam energy losses in a water layer on the sample surface were studied; consequently, the influence of the water thickness on radiation, temperature, or chemical damage of the sample was considered.

In Situ Observations and Measurements of Mechanically Induced Grain Boundary Migration in a Scanning Electron Microscope

2012 ◽  
Vol 715-716 ◽  
pp. 819-824 ◽  
Author(s):  
Tatiana Gorkaya ◽  
Thomas Burlet ◽  
Dmitri A. Molodov ◽  
Günter Gottstein
Keyword(s):  
Shear Stress ◽  
Grain Boundary ◽  
Elevated Temperatures ◽  
Boundary Migration ◽  
Grain Boundary Migration ◽  
Orientation Contrast ◽  
In Situ Observations ◽  
Set Up ◽  
Scanning Electron

A novel set-up developed to continuously observe and measure stress driven grain boundary migration is presented. A commercially available tensile/compression SEM unit was utilized for in-situ observations of mechanically loaded samples at elevated temperatures up to 850°C by recording orientation contrast images of bicrystal surfaces. Two sample holders for application of a shear stress to the boundary in bicrystals of different geometry were designed and fabricated. The results of first measurements are presented.

The evolution of grain-boundary cracking evaluated through in situ tensile-creep testing of Udimet alloy 188

2008 ◽  
Vol 23 (2) ◽  
pp. 500-506 ◽  
Author(s):  
C.J. Boehlert ◽  
S.C. Longanbach ◽  
M. Nowell ◽  
S. Wright
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Creep Deformation ◽  
Surface Deformation ◽  
Coincident Site Lattice ◽  
Tensile Creep ◽  
Face Centered Cubic ◽  
High Angle ◽  
Electron Backscattered Diffraction

In situ scanning electron microscopy was performed during elevated-temperature (⩽760 °C) tensile-creep deformation of a face-centered-cubic cobalt-based Udimet 188 alloy to characterize the deformation evolution and, in particular, the grain boundary-cracking evolution. In situ electron backscatter diffraction observations combined with in situ secondary electron imaging indicated that general high-angle grain boundaries were more susceptible to cracking than low-angle grain boundaries and coincident site-lattice boundaries. The extent of general high-angle grain-boundary cracking increased with increasing creep time. Grain-boundary cracking was also observed throughout subsurface locations as observed for postdeformed samples. The electron backscattered diffraction orientation mapping performed during in situ tensile-creep deformation proved to be a powerful means for characterizing the surface deformation evolution and in particular for quantifying the types of grain boundaries that preferentially cracked.

The Use of Advanced Analytical Techniques for Characterization of the Chemical, Physical, and Crystallographic Nature of a Surface

1973 ◽  
Vol 31 ◽  
pp. 132-133 ◽  
Author(s):  
R. E. Herfert
Keyword(s):  
Surface Characterization ◽  
Analytical Techniques ◽  
X Ray Diffraction ◽  
Depth Of Penetration ◽  
X Ray ◽  
The Past ◽  
Transmission Electron ◽  
Scanning Electron

Studies of the nature of a surface, either metallic or nonmetallic, in the past, have been limited to the instrumentation available for these measurements. In the past, optical microscopy, replica transmission electron microscopy, electron or X-ray diffraction and optical or X-ray spectroscopy have provided the means of surface characterization. Actually, some of these techniques are not purely surface; the depth of penetration may be a few thousands of an inch. Within the last five years, instrumentation has been made available which now makes it practical for use to study the outer few 100A of layers and characterize it completely from a chemical, physical, and crystallographic standpoint. The scanning electron microscope (SEM) provides a means of viewing the surface of a material in situ to magnifications as high as 250,000X.

Remarks on the application of backscattered electron imaging (BEI) to the scanning electron microscopy (SEM) of biological structures

1983 ◽  
Vol 41 ◽  
pp. 484-487
Author(s):  
Etienne de Harven
Keyword(s):  
High Resolution ◽  
Incident Beam ◽  
Spot Size ◽  
Primary Electron ◽  
Critical Point Drying ◽  
Cell Shapes ◽  
High Resolution Images ◽  
Backscattered Electron ◽  
Electron Imaging ◽  
Scanning Electron

Biological ultrastructures have been extensively studied with the scanning electron microscope (SEM) for the past 12 years mainly because this instrument offers accurate and reproducible high resolution images of cell shapes, provided the cells are dried in ways which will spare them the damage which would be caused by air drying. This can be achieved by several techniques among which the critical point drying technique of T. Anderson has been, by far, the most reproducibly successful. Many biologists, however, have been interpreting SEM micrographs in terms of an exclusive secondary electron imaging (SEI) process in which the resolution is primarily limited by the spot size of the primary incident beam. in fact, this is not the case since it appears that high resolution, even on uncoated samples, is probably compromised by the emission of secondary electrons of much more complex origin.When an incident primary electron beam interacts with the surface of most biological samples, a large percentage of the electrons penetrate below the surface of the exposed cells.

Observation of GaAs/AlAs Superlattice Structures in both Secondary and Backscattcred Electron Imaging Modes with an Ultrahigh Resolution Scanning Electron Microscope

1990 ◽  
Vol 48 (1) ◽  
pp. 404-405
Author(s):  
K. Ogura ◽  
A. Ono ◽  
S. Franchi ◽  
P.G. Merli ◽  
A. Migliori
Keyword(s):  
Gaas Layer ◽  
Objective Lens ◽  
Superlattice Structure ◽  
Backscattered Electron ◽  
Instrumental Resolution ◽  
Electron Microscopes ◽  
Superlattice Structures ◽  
Electron Imaging ◽  
Scanning Electron Microscopes ◽  
Scanning Electron

In the last few years the development of Scanning Electron Microscopes (SEM), equipped with a Field Emission Gun (FEG) and using in-lens specimen position, has allowed a significant improvement of the instrumental resolution . This is a result of the fine and bright probe provided by the FEG and by the reduced aberration coefficients of the strongly excited objective lens. The smaller specimen size required by in-lens instruments (about 1 cm, in comparison to 15 or 20 cm of a conventional SEM) doesn’t represent a serious limitation in the evaluation of semiconductor process techniques, where the demand of high resolution is continuosly increasing. In this field one of the more interesting applications, already described (1), is the observation of superlattice structures.In this note we report a comparison between secondary electron (SE) and backscattered electron (BSE) images of a GaAs / AlAs superlattice structure, whose cross section is reported in fig. 1. The structure consist of a 3 nm GaAs layer and 10 pairs of 7 nm GaAs / 15 nm AlAs layers grown on GaAs substrate. Fig. 2, 3 and 4 are SE images of this structure made with a JEOL JSM 890 SEM operating at an accelerating voltage of 3, 15 and 25 kV respectively. Fig. 5 is a 25 kV BSE image of the same specimen. It can be noticed that the 3nm layer is always visible and that the 3 kV SE image, in spite of the poorer resolution, shows the same contrast of the BSE image. In the SE mode, an increase of the accelerating voltage produces a contrast inversion. On the contrary, when observed with BSE, the layers of GaAs are always brighter than the AlAs ones , independently of the beam energy.

High-Resolution Resistance Mapping in SEM

2018 ◽  
Author(s):  
Grigore Moldovan ◽  
Wolfgang Joachimi ◽  
Guillaume Boetsch ◽  
Jörg Jatzkowski ◽  
Frank Altman
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
High Resolution ◽  
Reference Structure ◽  
Total Resistance ◽  
Embedded Electronics ◽  
Improved Performance ◽  
Mapping Techniques ◽  
Scanning Electron

Abstract This work presents advanced resistance mapping techniques based on Scanning Electron Microscopy (SEM) with nanoprobing systems and the related embedded electronics. Focus is placed on recent advances to reduce noise and increase speed, such as integration of dedicated in situ electronics into the nanoprobing platform, as well as an important transition from current-sensitive to voltagesensitive amplification. We show that it is now possible to record resistance maps with a resistance sensitivity in the 10W range, even when the total resistance of the mapped structures is in the range of 100W. A reference structure is used to illustrate the improved performance, and a lowresistance failure case is presented as an example of analysis made possible by these developments.

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