Browsing by Author "Mignone, PJ"
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- ItemMechanical properties of tungsten copper composites: direct measurement by neutron diffraction(Australian Institute of Physics, 2014-02-04) Mignone, PJ; Finlayson, TR; Kabra, S; Zhang, SY; Franks, GV; Riley, DPThe composite W-10 wt%Cu (19.35% by volume, assuming negligible porosity) has been studied using the ENGIN-X beamline at the ISIS pulsed neutron source at the Rutherford Appleton Laboratory. An as-machined, compression sample was initially measured in order to check for the presence of residual stresses in the composite, using a mixed powder sample of the same elemental weight fractions as the “zero stress” comparison. Then a series of mechanical tests were carried out on the composite for applied compressive loads up to 250 MPa at both room temperature and 100ºC and compared with similar tests carried out on pure tungsten and copper samples. Residual stress values of -280 MPa (for the tungsten matrix) and 480 MPa (for the copper particulate phase) were measured for the as-machined sample. This is a surprising result, given that the yield stress for copper is typically less than 100 MPa but is not inconsistent with residual stresses reported in the literature for W-Cu composites. The mechanical properties for the composite have also been determined from the results of these in-situ, mechanical tests and compared with finite element calculations based on microstructural models for the composite material.
- ItemA novel multi-scale modelling approach for determining the bulk properties of difficult-to-characterise composites(Australian Institute of Physics, 2013-02-05) Mignone, PJ; Wang, M; Finlayson, TR; Echlin, MP; Mottura, A; Pollock, TM; Riley, DP; Franks, GVA multi-scale modelling approach is presented for determining the bulk properties of copper-infiltrated Tungsten (W-Cu). A three-dimensional (3D) data-set of the W-Cu microstructure was generated using a novel serial-sectioning instrument. The image data were then reconstructed into a 3D Finite Element (FE) mesh. This made it possible to determine the bulk properties of W-Cu by simulating a representative volume of the microstructure.
- ItemThree-dimensional characterization of the permeability of W–Cu composites using a new “triBeam” technique(Elsevier, 2014-02) Echlin, MP; Mottura, A; Wang, M; Mignone, PJ; Riley, DP; Franks, GV; Pollock, TMLarge three-dimensional microstructural datasets have been gathered for two W–Cu composites of 10 and 15 wt.% Cu using the TriBeam 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 μm to 160 μm on edge. The converged values of the volume fractions of Cu closely match experimental values measured by the Archimedes technique.© 2013 Acta Materialia Inc.