Three-dimensional characterization of the permeability of W-Cu composites using a new "TriBeam" technique

Large three-dimensional microstructural datasets have been gathered for two W-Cu composites of 10 and 15 wt.% Cu using the Tri-Beam system via in situ femtosecond laser sectioning in a scanning electron microscope. Laser ablation was performed on W-Cu samples along a 90 edge, milling parallel with the imaging surface. Secondary electron images for 1000 two-dimensional slices were segmented into binary images representing Cu and W components using EM/MPM (expectation maximization/maximization of the posterior marginals) image-processing algorithms. A statistically random volume sampling approach has been employed to evaluate the microstructural and property volume element sizes necessary for the assessment of volume fraction, surface-area to volume ratio and permeability, respectively. This approach also characterizes the mean values and variability in microstructure and properties for volume elements ranging from 10 mu m to 160 mu m on edge. The converged values of the volume fractions of Cu closely match experimental values measured by the Archimedes technique. (C) 2013 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.