3DXDM: 3-Dimensional X-Ray Diffraction Microscopy

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3DXDM3-Dimensional X-Ray Diffraction Microscopy

• By Ivan Lopez and Michael Ubowski
• Advisors Dr. Robert Suter
• Dr. Francine Papillon
• Graduate Advisors Dan Hennessy
• Chiangshi Xiao
• August 6, 2004
• CMU-MRSEC

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Goal/Introduction 3DXDM

• To create a non-destructive method of obtaining a
  materials microstructure.
• Allows for the texture mapping of changes in
  microstructure due to
• Heat Treatments
• Fractures
• Plastic Deformation

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Experimental Setup
Detector
Beam Stop
1mm Diameter Sample
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Experimental Setup
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Michaels Project Goal

• Determine the Texture of individual grains
• Characterize the cause of the texture as
• Stresses within grains
• Dislocations
• Combination of both

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Approach

• Obtain the grain orientation based on analysis of
  1 interval diffraction images.
• Compare with data taken at 1/100 degree
  intervals.
• Characterize grains as splayed or almost perfect
  blocks.
• Splayed planes are stresses.
• Almost perfect block planes have dislocations.

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Aluminum Single Crystal Analysis

• Pre and Post Annealed Data.
• Eight Layers at 100 rotations per layer.
• Data is first analyzed using an image enhancement
  program and then simulated using a Monte Carlo
  fitting technique.
• Color maps of different layers in the
  pre-annealed data set show possible trend.

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Average Mis-Orientation

• Comparison of average mis-orientation between Pre
  and Post annealing.
• Decreases in average mis-orientation yields
  relief in stresses and dislocations.
• Average mis-orientation based on overall average
  orientation
• Results show that our technique maybe be able
  detect the difference.

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Future Work

• Analyze the 1/100 degree data.
• Compare Results with 1 interval data.
• Characterize the texture.

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MgO Sample Goal

• To characterize and eliminate the diffuse
  scattering, caused by segregation of an amorphous
  phase (Si and Ca oxides) at the grain boundaries,
  in order to extract diffraction spots from that
  region.

L1
L2
L3
z Layer 1 w 48o
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Approach/Results I

• Average images with similar diffuse scattering
  and subtract that from each image along with the
  background.

L1
L2
L3
z Layer 1 w 48o
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Difficulties/Problems I

• Intensity of the diffuse scattering increases
  with each layer (z-direction) and with each w
  while the intensities of the diffraction spots
  remain quite constant.

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Difficulties/Problems I

• Diffuse scattering does not subtract in deeper
  layers, as can be seen by MgO-1250 (5th Layer)
  before and after.

• Nature of the spot changes throughout each set
  of detector images due to the procedure in which
  the images were taken.

Before
After
z Layer 5 w 50o
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Approach/Results II

• Fit a function to the curve of the intensity and
  subtract this from the image.
• Polynomials of various degrees were used.

L1
z Layer 1 w 48o
z Layer 5 w 50o
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Difficulties/Problems II

• For some images the nature of the Spot didnt
  allow for an accurate polynomial fit.
• Spots are left that are not true diffraction
  spots.
• Simulation will hopefully disregard these
  artificial spots.

L1
z Layer 8 w 25o
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Fluorescence

• Atoms within the sample absorb energy (photons)
  from the incident beam and reach an excited
  state. Upon returning to stable states, the
  atoms emit more photons.

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Filtering the Fluorescence

• Insert a filter between the sample and the
  detector.
• Filter used was a piece of computer printer paper
  taped over the detector.

With Filter
Without Filter
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Future work

• Run a simulation of the cleaned up Mgo data set.
• Next APS visit, obtain a detailed MgO data set
  with the filter in place.

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APS Pictures
Questions?