There exists significant prior work using tracers or pre-placed hardened markers within FSW to experimentally explore material flow within the FSW process.  Our experiments replaced markers with a thin sheet of copper foil placed between the 6061 Aluminum lap and butt joints that were then welded.  The absorption characteristics of x-rays for copper and aluminum are significantly different allowing for non-destructive evaluation (NDE) methods such as x-ray computed tomography (CT) to be used to demonstrate the material movement within the weldment on a much larger scale than previously shown.   3D CT reconstruction of the copper components of the weldment allows for a unique view into the final turbulent state of the welding process as process parameters are varied.  The x-ray CT data of a section of the weld region was collected using a cone-beam x-ray imaging system developed at the INL.  Six-hundred projections were collected over 360-degrees using a 160-kVp Bremsstrahlung x-ray generator (25-micrometer focal spot) and amorphous-silicon x-ray detector.  The region of the object that was imaged was about 3cm tall and 1.5cm x 1cm in cross section, and was imaged at a magnification of about 3.6x.  The data were reconstructed on a 0.5x0.5x0.5 mm3 voxel grid.  After reconstruction, the aluminum and copper could be easily discriminated using a gray level threshold allowing visualization of the copper components.  Fractal Analysis of the tomographic reconstructed material topology is investigated as a means to quantify macro level material flow based on process parameters.  The results of multi-pass FSWs show increased refinement of the copper trace material.  Implications of these techniques for quantifying process flow are discussed.