Advanced Engineering Materials

Cover image for Vol. 8 Issue 6

Special Issue: X-ray Microtomography

June, 2006

Volume 8, Issue 6

Pages 451–584

Issue edited by: Eric Maire

    1. Cover Picture: The Role of Oxidation During Compaction on the Expansion and Stability of Al Foams Made Via a PM Route (Adv. Eng. Mater. 6/2006)

      S. Asavavisithchai and A. R. Kennedy

      Version of Record online: 28 JUN 2006 | DOI: 10.1002/adem.200690011

      The foam expansion and collapse behaviour for hot compacted Al-TiH2 precursors has been shown to be driven by the oxidation of the Al powder and the premature loss of gas from the TiH2 foaming agent during the compaction process. At 550 °C, oxidation is rapid, and gas loss from the hydride is extensive leading to poor expansion.

    2. Contents: Adv. Eng. Mater. 6/2006 (pages 451–455)

      Version of Record online: 28 JUN 2006 | DOI: 10.1002/adem.200690010

    3. 3-D Image-Based Mechanical Simulation of Aluminium Foams: Effects of Internal Microstructure (pages 459–467)

      H. Toda, M. Takata, T. Ohgaki, M. Kobayashi, T. Kobayashi, K. Uesugi, K. Makii and Y. Aruga

      Version of Record online: 28 JUN 2006 | DOI: 10.1002/adem.200600035

      Synchrotron radiation X-ray microtomography has been utilized for the 3D characterization of microstructures in an aluminium foam. Both quasi-static and dynamic deformation and damage behaviours are investigated by means of a 3-D image-based finite-element simulation. The approach taken in this study has provided effective ways to characterize microstructure/properties relationships in such heterogeneous materials.

    4. 2D and 3D Visualization of Ductile Fracture (pages 469–472)

      A. Weck, D. S. Wilkinson, H. Toda and E. Maire

      Version of Record online: 28 JUN 2006 | DOI: 10.1002/adem.200600034

      New model materials made of laser drilled copper sheets have been fabricated to study the ductile fracture process. In-situ tensile tests in a scanning electron microscope and in an X-Ray computed tomography set-up allows us to observe the void growth and coalescence in 2D and 3D. It is shown that there are different modes of coalescence depending on the voids geometry and that constraining effects in the 3D case allow more void growth prior coalescence.

    5. In-situ High-resolution X-ray CT Observation of Compressive and Damage Behaviour of Aluminium Foams by Local Tomography Technique (pages 473–475)

      T. Ohgaki, H. Toda, M. Kobayashi, K. Uesugi, T. Kobayashi, M. Niinomi, T. Akahori, K. Makii and Y. Aruga

      Version of Record online: 28 JUN 2006 | DOI: 10.1002/adem.200600039

      Cellular aluminium foams exhibits complicated structures. 3D analysis is therefore of crucial importance to improve mechanical performance of such foams. The aim of this study was to investigate the compressive and damage behaviour of Al foams. Using the local tomography technique and an in-situ test rig, the relations between microstructural features and fracture behaviour were assessed by the 3D local strain mapping.

    6. X-ray Microtomographic Characterisation of Porosity and its Influence on Fatigue Crack Growth (pages 476–479)

      P. Li, P. D. Lee, T. C. Lindley, D. M. Maijer, G. R. Davis and J. C. Elliott

      Version of Record online: 28 JUN 2006 | DOI: 10.1002/adem.200600051

      Cast Al alloys are seeing increasing use in transport applications due to their high strength-to-weight ratio at an acceptable cost compared to many ferrous alloys. Therefore, a quantitative characterisation of the pore distribution and its influence on the evolution of fatigue damage are required to predict the fatigue life of cast Al alloy components. In this investigation, X-ray microtomography was used to characterise the 3D morphology of porosity in A356-T6 specimens and to relate the porosity to fatigue behaviour.

    7. X-ray Microtomography Analysis of Dynamic Damage in Tantalum (pages 480–486)

      J. Bontaz-Carion and Y.-P. Pellegrini

      Version of Record online: 28 JUN 2006 | DOI: 10.1002/adem.200600058

      With the plate-impact technique, ductile spallation experiments are carried out on Ta at impact velocities 570, 1039 and 1078 m/s. Samples are soft-recovered and analyzed by X-Ray microtomography at the European Synchrotron Radiation Facility. The porosity along the shock direction, and the distribution of the pore volumes are extracted from tri-dimensional reconstructions of the damaged samples. Quantitative assessment of pore coalescence is made via an inverse power-law model for the distribution. The decay exponent we associate to coalescence is of order 1.6 in the sample impacted at 1039 m/s.

    8. Validation of Marker Material Flow in 4mm Thick Friction Stir Welded Al 2024-T351 through Computer Microtomography and dedicated Metallographic Techniques (pages 487–490)

      R. Zettler, T. Donath, J. F. dos Santos, F. Beckman and D. Lohwasser

      Version of Record online: 28 JUN 2006 | DOI: 10.1002/adem.200600062

      This study forms part of a joint three year project between the GKSS-Forschungszentrum and Airbus Deutschland titled “Effect of material flow patterns on the properties of friction stir welds in aluminium alloys for aircraft structures” -EMFASIS. The global aim of our research project is to identify how process and geometric parameters such as weld tool geometry influence the weld energy and subsequent joint properties of four friction stir welded aerospace grade aluminium alloys. The current study reports on the visualisation and displacement of a Ti powder marker material dispersed within the weld zone and investigated with the aid of X-ray computer microtomography (μCT) and dedicated metallographic techniques.

    9. Characterization of Lightweight Graphite Based Composites Using X-Ray Microtomography (pages 491–495)

      S. A. Sánchez, J. Narciso, F. Rodríguez-Reinoso, D. Bernard, I. G. Watson, P. D. Lee and R. J. Dashwood

      Version of Record online: 28 JUN 2006 | DOI: 10.1002/adem.200600101

      X-ray Micro-Tomography is an important technique that has been developed during the last years. This characterization tool can be applied to graphite/aluminium composites obtaining 3D microstructural information from the reconstruction of 2D X-ray transmission images. The resulting volume data set can be used as model for simulating properties or understanding the behavior of the material.

    10. Analysis of Tomography Images of Bonded Fibre Networks to Measure Distributions of Fibre Segment Length and Fibre Orientation (pages 495–500)

      J. C. Tan, J. A. Elliott and T. W. Clyne

      Version of Record online: 28 JUN 2006 | DOI: 10.1002/adem.200600033

      The architecture of bonded fibre networks produced by sintering of short stainless steel fibres has been characterised using computed X-ray microtomography. Two important characteristics of such networks are the distributions of fibre segment length and fibre orientation. These have strong influences on the mechanical, thermal and electrical properties. To extract quantitative architectural data from the reconstructed fibre networks, a 3-D skeletonisation algorithm was used to convert the reconstructed fibre surfaces into their corresponding medial axes.

    11. Estimation of Elastic Properties of Particle Reinforced Metal-Matrix Composites Based on Tomographic Images (pages 500–506)

      P. Kenesei, H. Biermann and A. Borbély

      Version of Record online: 28 JUN 2006 | DOI: 10.1002/adem.200600042

      The structure of a real particle reinforced metal-matrix composite, Al/Al2O3, was retrieved by high resolution X-ray tomography. The paper presents a study of the influence of local structure variability on the elastic properties of the composite. The results are in good agreement with theoretical two-point bounds.

    12. Mean Field and Multiscale Modeling of a Particle Reinforced Metal-Matrix Composite Based on Microtomographic Investigations (pages 506–510)

      P. Kenesei, A. Klohn, H. Biermann and A. Borbély

      Version of Record online: 28 JUN 2006 | DOI: 10.1002/adem.200600040

      Based on evaluations of 3-D X-ray microtomographic reconstructions simple mean-field and multi-scale models were developed for predicting the plastic response of particle reinforced metal-matrix composites. It is shown that increasing heterogeneity, by taking more details of the microstructure into account, leads to stress-strain curves, which differ only slightly from the curve of the mean-field model.

    13. Anodizing Treatments for Magnesium Alloys and Their Effect on Corrosion Resistance in Various Environments (pages 511–533)

      C. Blawert, W. Dietzel, E. Ghali and G. Song

      Version of Record online: 28 JUN 2006 | DOI: 10.1002/adem.200500257

      A ceramic like anodised coating can effectively prevent Mg alloys from corrosion. Its porous microstructure offers a great base for organic coatings. Anodising should be one of the most practical and effective surface treatments for magnesium alloys. This paper reviews the basics, processes, properties and applications of anodising techniques of Mg alloys.

    14. Integrated Approach for the Development of Advanced, Coated Gas Turbine Blades (pages 535–562)

      R. Herzog, N. Warnken, I. Steinbach, B. Hallstedt, C. Walter, J. Müller, D. Hajas, E. Münstermann, J. M. Schneider, R. Nickel, D. Parkot, K. Bobzin, E. Lugscheider, P. Bednarz, O. Trunova and L. Singheiser

      Version of Record online: 28 JUN 2006 | DOI: 10.1002/adem.200500277

      This article describes an integrative through-process modelling approach on a microstructural level of the production of a coated turbine blade (casting, coating processes) including its in-service properties and degradation, accompanied by the actual production and testing of a CMSX-4 single crystal turbine blade dummy. This work forms a part of the Collaborative Research Centre 370 (SFB 370) “Integrative materials modelling”.

    15. Combustion Characteristics of Mechanically Alloyed Ultrafine-Grained Al-Mg Powders (pages 563–567)

      R.-H. Chen, C. Suryanarayana and M. Chaos

      Version of Record online: 28 JUN 2006 | DOI: 10.1002/adem.200600002

      The combustion characteristics of ultrafine Al-Mg alloy powder particles, produced by mechanical alloying methods, and sieved to well-defined size ranges (35 to 100 μm) were investigated. The ignition and burning times and their size-dependence were determined using time-resolved images of particles burned in the post-flame zone. It was observed that both the ignition and burning times increased with increasing particle size.

    16. The Role of Oxidation During Compaction on the Expansion and Stability of Al Foams Made Via a PM Route (pages 568–572)

      S. Asavavisithchai and A. R. Kennedy

      Version of Record online: 28 JUN 2006 | DOI: 10.1002/adem.200500245

      The foam expansion and collapse behaviour for hot compacted Al-TiH2 precursors has been shown to be driven by the oxidation of the Al powder and the premature loss of gas from the TiH2 foaming agent during the compaction process. At 550 °C, oxidation is rapid, and gas loss from the hydride is extensive leading to poor expansion.

    17. Synthesis of Nb Doped Lead Zirconate Titanate by Chemical Methods (pages 572–576)

      A. L. Costa, G. Montanari, C. Galassi, M. Cernea, F. Bezzi and S. Albonetti

      Version of Record online: 28 JUN 2006 | DOI: 10.1002/adem.200500235

      This paper shows the results of different chemical syntheses: sol-gel, spray-drying, coprecipitation, involved in the production of niobium doped lead zirconate titanate ceramic materials. The formation of pure perovskitic phase at temperatures 300–400 °C lower than the traditional mixed oxide method confirmed the potentiality of the spray-drying and sol-gel as simple synthesis processes to produce chemically homogeneous and very reactive powders. The thermal and structural evolution of precursor powders was investigated through TG/DTA, IR and XRD analyses. The microstructures of powders and sintered bodies were presented and related to the synthesis process.

    18. Control over Cement Setting Through the Use of Chemically Modified Fly Ash (pages 576–580)

      C. Lupu, K. L. Jackson, S. Bard, I. Rusakova and A. R. Barron

      Version of Record online: 28 JUN 2006 | DOI: 10.1002/adem.200500280

      The chemical treatment of Class C fly ash with a 0.2 wt% of CaCO3 solution results in dramatic increase in setting time and superior stability during the induction period for cement slurries at temperature conditions relevant for down-hole applications. The performance of the CaCO3 treatment appears to be a consequence of each fly ash particle being provided with the necessary Ca prior to hydration without being dependant on cement-fly ash particle interactions. Thus, the setting process is no longer dependent on the particle shape, packing and dispersion of the fly ash and cement. That with the extended setting times, the induction period follows almost ideal shape is most important for oil well applications where it is necessary to pump a specific viscosity slurry over large distances within a specific time, without changes in viscosity that would effect pump rates.

    19. Periodical Surface Structuring of Metals by Laser Interference Metallurgy as a New Fabrication Method of Textured Solar Selective Absorbers (pages 580–584)

      A. Lasagni, F. Mücklich, M. R. Nejati and R. Clasen

      Version of Record online: 28 JUN 2006 | DOI: 10.1002/adem.200500261

      Spectral emittance and absorptance of copper and stainless steel surface gratings for photo-thermal solar absorbers were studied. The samples were produced by Laser Interference Metallurgy which is an alternative to produce periodical structures with remarkable advantages. Spectral properties of the structured samples indicates that the larger the aspect ratio, the better the solar absorptance. Due to the small period of the structures, thermal emittance didn't increase considerably at room temperature.

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