Advanced Materials Characterization Labs
EBSD Evaluation
The new DigiView camera and software system from TSL does work on the
S4700. This is not to say that there are not problems encountered while working
with the system. I examined approximately three samples for this evaluation. One
sample was a friction stir weld from Siddarth Sharma , and two where single
crystal gold samples. There were several software and hardware issues
encountered that were not resolved.
Results
A scan was conducted on a Au single crystal, when the system exhibited several
indexed patterns correctly with good statistics in succession.
Here is the grayscale map or the Image Quality map of that
scan:
This image shows the scratches and some surface crud on
the Au single crystal. A texture plot of the data was done:
A second single Au crystal was examined. Here is the texture plot for that crystal:
The data showed in these texture plots corresponds to the data obtained from the XRD
system. The next step in the project was to put a coating on the gold crystals and to see if
the system could distinguish two chiral patterns. This did not happen as the camera stop
working for the second run on July 26th.
Prior to the camera being down a second sample type was examined. A friction stir weld
was examined at the top of the sample in the weld area and also in the middle below the
weld area.
The top scan had 3088 points with 3031 good points. The size of the scan was
139microns by 19.05 microns with a 1 micron step size. The average Confidence Index
was 0.23, average Image Quality was 42.32 and the average fit was 1.64.
The oim maps from the top scan are below: The IPF, or inverse pole figure map, appears
to be a double map.
This is due to the fact the area selected in the original scan was larger than the viewing
area of the software. The grains are clear and distinct. The grain size below 12 microns.
The gray scale map shows the grain boundaries much better than the IPF map. The pole
figure for the data collects suggest a texture is present in the weld area.
Pole Figure
Texture Plot
The second scan area 17111 point with 17106 good points. The size of the
scanned area was 30 microns by 30 microns with a step size of 0.25 microns. The
Average Confidence Index was 0.52, the average Image Quality was 78.55, and the
average Fit was 1.15, with better map statistics.
The IPF map appears to shows much larger grains present:
The grains are not bigger but the
area scanned is much smaller.
The gray scale map shows grain boundaries very well.
As with the area of the friction stir weld the texture plot suggest some texture
present in this area of the sample.
Problems
1) The indexing was poor or no solution was found even with the pattern was
visible.
This pattern also shows that
the indexing lines were off and
that some of the lines were not
indexed at all.
Some of the other problems
encountered during this
evaluation are listed in detail
below.
2) This problem occurred in previous attempts to collect patterns. It was seen mainly in
when the binning was 4X4.
Another problem was that during indexing there were lines not indexed that were present
in the pattern. In the figure below the line that goes across the upper right is not identified
in the indexing of the pattern.
3) Another issue that was noticed was that during some of the indexing the lines did not
continue across the pattern, which can be seen in the previously indexed Au pattern. When
the working distance was change the lines and the indexing would change.
Only the working distance was changed in this next image.
The patterns could then be indexed correctly but the working distance was not
correct.
4) Also when trying to check the calibration the x, y, and z star kept changing.
As can be seen in the data from an Au scan:
Scan1
Operator: Administrator
Calibration: -0.027712 1.437666 1.534127
Working Distance: 19.000000
Number of points: 3182
Number of good points: 3170
Dimensions:
X Min: 0.00 microns
X Max: 31.00 microns
Y Min: 0.00 microns
Y Max: 86.60 microns
Step: 1.00 microns
Average Confidence Index: 0.08
Average Image Quality: 197.13
Average Fit [degrees]: 1.90
Minimum boundary misorientation: 2.0 degrees (see Settings>Preferences)
Number of boundary segments: 1506
Length of boundary segments: 869.489 microns
Phases:
Gold
The statistics from this scan are terrible and the x, y, and z star are way off of the
calibration that is 47.00, 69.00 and 77.04. This is probably what led to the poor
statistics of this scan.
5) There was also a problem with the indexing of the pattern being rotated from
the pattern:
The 101 point is at the bottom of this pattern not at the upper left. Also causing
poor statistics. This was checked with the simulation portion of the software.
6) One of the most reoccurring problems encountered was a spot in the video
image. Setting of the scope and the camera parameters will probably be the cure
for this particular issue.
7) The DigiView camera at times did not work, and errors were displayed on the
screen, as seen below:
This happened on July 18th and July 26th while operating the system to obtain
images. The makers of DigiView, and also TSL, were called on July 18th for help
in resolving this problem. The power supply for the camera was not operating, so
it was un-plugged and plugged back into the wall socket. This was repeated several
times until the camera power supply stayed on. The second time this problem
showed up the camera error message did not appear after the unplugging and replugging the camera power supply. An pattern image could not be obtained from a
previously imaged sample. The video image was flickering very rapidly and the
gain could not be set. Every time it was changed the flickering went darker or
lighter. Turned off the MSC 2200 and the computer to see if this would somehow
reset the camera but the flickering remained after the re-boot.
TSL sent some information on the operation of the system, after the first carmea
issue, and these were instituted. The system started to obtain patterns but the
indexing was way off. This lead to the thinking that the calibration was off. The
calibration was checked and the Pattern Center, or PC, was off the pattern. The PC
was corrected to the original values when the system was installed and the
indexing was better. The change in the calibration sometimes did not stay when a
new pattern was obtained even though it was recorded. The indexing was poor or
no solution was found even with the pattern was visible.
Conclusion
The new TSL system does produce better and more consistent patterns for
indexing and OIM. Although a small grain sample was not examined, it was
thought that the friction stir weld would have small grains; the system did very
well on Al. The SEM parameters do need to be changed to allow more energy to
reach the sample. With time and more experience a good technique can be
developed to EBSD on most of the samples that have thus far been submitted to the
lab. A ceramic sample was tried but no patterns were obtained. Sample prep for
ceramics will be more in-depth than even those for metallic samples. The
simulation portion of the software proved to very helpful in determining
orientations for other than OIM samples.
Over coming the problems could be done with an actual released version of the
software and not a beta version.