scholarly journals Determination of Long-Range Internal Stresses in Cyclically Deformed Copper Single Crystals Using Convergent Beam Electron Diffraction

Crystals ◽  
2020 ◽  
Vol 10 (12) ◽  
pp. 1071
Author(s):  
Roya Ermagan ◽  
Maxime Sauzay ◽  
Matthew H. Mecklenburg ◽  
Michael E. Kassner

Understanding long range internal stresses (LRIS) may be crucial for elucidating the basis of the Bauschinger effect, plastic deformation in fatigued metals, and plastic deformation in general. Few studies have evaluated LRIS using convergent beam electron diffraction (CBED) in cyclically deformed single crystals oriented in single slip and there are no such studies carried out on cyclically deformed single crystals in multiple slip. In our earlier and recent study, we assessed the LRIS in a cyclically deformed copper single crystal in multiple slip via measuring the maximum dislocation dipole heights. Nearly equal maximum dipole heights in the high dislocation density walls and low dislocation density channels suggested a uniform stress state across the labyrinth microstructure. Here, we evaluate the LRIS by determining the lattice parameter in the channels and walls of the labyrinth dislocation structure using CBED. Findings of this work show that lattice parameters obtained were almost equal near the walls and within the channels. Thus, a homogenous stress state within the heterogeneous dislocation microstructure is again suggested. Although the changes in the lattice parameter in the channels are minimal (less than 10−4 nm), CBED chi-squared analysis suggests that the difference between the lattice parameter values of the cyclically deformed and unstrained copper are slightly higher in the proximity of the walls in comparison with the channel interior. These values are less than 6.5% of the applied stress. It can be concluded that the dominant characteristics of the Bauschinger effect may need to include the Orowan-Sleeswyk mechanism type of explanation since both the maximum dipole height measurements and the lattice parameter assessment through CBED analysis suggest a homogenous stress state. This work complements our earlier work that determined LRIS based on dipole heights by assessing LRIS through a different methodology, carried out on a cyclically deformed copper single crystal oriented for multiple slip.

1994 ◽  
Vol 343 ◽  
Author(s):  
S. K. Streiffer ◽  
S. Bader ◽  
C. Deininger ◽  
J. Mayer ◽  
M. Rühle

ABSTRACTStrains in polycrystalline Al films grown on oxidized Si wafers were measured using convergent beam electron diffraction (CBED). CBED patterns were acquired on a Zeiss EM 912 TEM equipped with an imaging energy filter and CCD camera. HOLZ line positions in the (000) CBED disk were matched using an automated refinement procedure. A sensitivity to variations in lattice parameter of approximately 0.00007 nm was obtained. Strong deviations from a simple equibiaxial strain, perfect [111] texture model were observed.


1986 ◽  
Vol 69 ◽  
Author(s):  
M. E. Twigg ◽  
S. N. G. Chu ◽  
D. C. Joy ◽  
D. M. Maher ◽  
A. T. Macrander ◽  
...  

AbstractWith X-ray diffraction techniques, it is possible to routinely measure lattice parameters to several parts in 104 for macroscopic specimens. However, measurements of lattice parameter changes for quaternary (InGaAsP) device structures several microns in width are not usually feasible with X-ray diffraction techniques. Convergent Beam Electron Diffraction (CBED), which is one of the techniques available on a modern transmission electron microscope (TEM), may be sensitive to these small, localized lattice parameter changes. Unfortunately, dynamical diffraction effects prevent direct extraction of changes in the lattice parameter from CBED patterns which are obtained from high atomic number materials. For this reason, we have chosen to calibrate the relative position of CBED features with X-ray lattice parameter measurements which were obtained from planar quaternary layers grown on InP substrates. For the active quaternary region of an electro-optical device structure, it is shown that this approach may be sensitive to a relative change in the lattice parameter as small as ±2 parts in 104, which is the uncertainty in the X-ray calibration measurements.


2008 ◽  
Vol 388 ◽  
pp. 273-276 ◽  
Author(s):  
Keisuke Kobayashi ◽  
Toshimasa Suzuki ◽  
Youichi Mizuno

The nanoscale local structure of core-shell structured BaTiO3 grains with a nonuniform dopant distribution was studied by convergent beam electron diffraction. The direct measurements of the variation of lattice parameter in an individual BaTiO3 grain were achieved. It was found that the lattice parameter continuously increased from inside the grain core to the grain shell and there was no discontinuity at the core/shell interface. The increasing gradient of c-axes was slightly smaller than that of a-axes, suggesting that the perovskite unit cell in the grain shell has lower tetragonality.


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