Marcus' research is focused on high energy x-ray diffraction measurements of materials using the Advanced Photon Source (APS) at Argonne National Laboratories. The work is taking place at the Synchrotron Radiation Instrumentation Collaborative Access Team (SRI-CAT) of APS, under the co-supervision of Dr. Dean Haeffner. The current research combines x-ray imaging with these high energy x-ray diffraction measurements.
One project involves interpenetrating phase composites (IPCs), which are characterized by two co-continuous and percolating phases. Al2O3 towers, consisting of 30 alternating 0/90° layers of parallel rods, are produced by robotic deposition using a gel-based ink at the University of Illinios at Urbana-Champaign by Jennifer Lewis' group.
FIGURE 1: (a) Side view of alumina tower with simple-cubic symmetry (rod diameter is ca. 250 μm ) and (b) an idealized 3-D schematic of the tower.
Once these towers are sintered, an interpenetrating Al2O3-Al composite is formed by liquid metal infiltration:
FIGURE 2: Pressure Infiltration Schematic
The resulting IPCs are subjected to uniaxial compressive stresses while internal strains are measured by synchrotron x-ray diffraction. The extent of load transfer between the two phases is measured for each preform geometry. The general set-up for these experiments is shown schematically in Figure 3. Of course, the schematic for imaging is not included and the mechanical testing (compressive loading, tensile loading, and bending) varies, but the principles are the similar.
FIGURE 3: Schematic of experimental setup.
FIGURE 4: A typical X-ray diffraction pattern for interpenetrating Al/alumina phase composites. Complete rings belong to the alumina, zirconia, and ceria phases, while partial rings belong to the Al phase.
The lattice strains from the diffracted rings recorded by the camera are determined by using Fit2D in conjunction with custom Matlab programs. The elastic lattice strain for (300) planes vs. the applied stress for an interpenetrating Al/Al2O3 phase composites is shown in Figure 3. Similar plots were obtained for other hkl planes as well
FIGURE 5: Applied stress vs. lattice strain for Al/alumina composites with simple-cubic symmetry, using (300) reflection, (a) upon increasing the stress (mechanical loading); (b) upon decreasing the stress (mechanical unloading).
From these data, load transfer between the aluminum and alumina phases can be observed. Note that residual strains are present under zero applied stress, as expected from the mismatch in thermal expansion between the two phases. In the future we intend to analyze different (hkl) planes for March 7, 2005are these results with Eshelby modeling, and perform detailed finite-element analysis using ABAQUS.
Related Publications
- R. Vaidyanathan, M.A.M. Bourke, D.C. Dunand. "Analysis of Neutron Diffraction Spectra Acquired In-Situ During Stress-Induced Transformations in Superelastic NiTi", Journal of Applied Physics A, 86, 6, 3020-3029 (1999).
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- A. Wanner, D.C. Dunand. "Synchrotron X-Ray Study of Bulk Lattice Strains in Externally-Loaded Cu-Mo Composites", Metallurgical and Materials Transactions A, 31A, 11, 2949-2962 (2000).
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- A. Wanner, D.C. Dunand. "Methodological Aspects of the High Energy Synchrotron X-ray Diffraction Technique for Internal Stress Evaluation", Journal of Neutron Research, 9, 2-4, 495-501 (2001).
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- D. Balch, E. Ustundag, D.C. Dunand. "Diffraction Strain Measurements in a Partially Crystallized Bulk Metallic Glass Composite Containing Ductile Particles", Journal of Non-Crystalline Solids, 317, 1-2, 176-180 (2003).
- C. San Marchi, M. Kouzeli, R. Rao, J.A. Lewis, D.C. Dunand. "Alumina-Aluminum Interpenetrating-Phase Composites with Three-Dimensional Periodic Architecture",Scripta Materialia 49, 9, 861-866 (2003).
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Financial Support
This research is funded by Argonne National Laboratory.
