Advanced Engineering Materials

Cover image for Advanced Engineering Materials

June, 2004

Volume 6, Issue 6

Pages 358–459

    1. Processing of Titanium Foams (pages 369–376)

      D. C. Dunand

      Version of Record online: 1 JUL 2004 | DOI: 10.1002/adem.200405576

      Because of their excellent mechanical properties, low density and biocompatibility, titanium foams are attractive for structural and biomedical applications. This paper reviews current techniques for titanium foam processing, which are all based on powder-metallurgy because of the extreme reactivity of liquid titanium. A first group of processes is based on powder sintering with or without place-holder or scaffolds. A second group relies on expansion of pressurized pores created during prior powder densification.

    2. Fabrication of Lotus-type Porous Metals and their Physical Properties (pages 377–384)

      H. Nakajima, T. Ikeda and S.K. Hyun

      Version of Record online: 1 JUL 2004 | DOI: 10.1002/adem.200405149

      Lotus-type porous metals whose were fabricated by unidirectional solidification in a pressurized gas atmosphere. The lotus-type porous metals with homogeneous size and porosity of the evolved pores can be obtained by mould casting. However, only porous metals and alloys with inhomogeneous porosity and pore size are produced for metals and alloys with low thermal conductivity such as stainless steel. In order to obtain uniformity of the porous metals, a new “continuous zone melting technique” was developed to fabricate long rod- and plate-shape porous metals and alloys even with low thermal conductivity.

    3. Endogenous Particle Stabilization During Magnesium Integral Foam Production (pages 385–390)

      C. Körner, M. Hirschmann, V. Bräutigam and R.F. Singer

      Version of Record online: 1 JUL 2004 | DOI: 10.1002/adem.200405147

      The production of magnesium integral foam components with a dense shell and a porous core is investigated. High pressure casting methods are used where liquid magnesium mixed with a blowing agent is injected into a permanent steel mould. A compact shell develops due to fast cooling at the walls. The resulting integral foams show a high weight-specific stiffness combined with high energy absorption capability. For the first time, foam stabilizing without additives is realized.

    4. Potential New Matrix Alloys for production of PM Aluminium Foams (pages 391–396)

      D. Lehmhus and M. Busse

      Version of Record online: 1 JUL 2004 | DOI: 10.1002/adem.200405146

      The powder compact melting technique for aluminium foam production as practized today accepts a certain mismatch between foaming agent decomposition and matrix alloy melting temperatures. This mismatch is believed to influence the pore structure in an unfavourable way. Adjustment of TiH2 decomposition as well as liquidus and solidus temperatures of matrix alloys can be used to counteract it.

    5. Production of Metallic Foams From Ceramic Foam Precursors (pages 397–399)

      A. Verdooren, H.M. Chan, J.L. Grenestedt, M.P. Harmer and H.S. Caram

      Version of Record online: 1 JUL 2004 | DOI: 10.1002/adem.200405150

      A process has been developed for obtaining closed cell metallic foams using a ceramic foam precursor. In this approach, the major constituent of the ceramic foam precursor is iron oxide, which is mixed with various foaming/setting additives. The mixture sets rapidly at room temperature to stabilize the foam generated by hydrogen release. The oxide foam is then reduced in a non-flammable hydrogen/inert gas mixture to obtain a metallic foam with a cell diameter of 0.5–2 mm.

    6. Effect of Ceramic Particle Additions on Foam Expansion and Stability in Compacted Al-TiH2 Powder Precursors (pages 400–402)

      A.R. Kennedy and S. Asavavisithchai

      Version of Record online: 1 JUL 2004 | DOI: 10.1002/adem.200405145

      Al2O3, SiC and TiB2 particles have been added to Al-TiH2 powder mixtures. The resulting precursors were foamed and it was found that by adding as little as 3 vol. % of particles, the maximum foam expansion was increased. Microstructural investigations revealed that particles enhance foam expansion through a reduction in the critical cell wall thickness before rupture. The presence of oxide in the molten powder system tends to prevent good wetting, the ceramic phase is usually located at the cell walls, protruding into the cells and does not prevent drainage of liquid through the cell structure. An exception to this case was observed in the Al-SiC system where wetting is good and enhanced by reaction between the two phases.

    7. Porous TiNi Biomaterial by Self-Propagating High-Temperature Synthesis (pages 403–406)

      J.S. Kim, J.H. Kang, S.B. Kang, K.S. Yoon and Y.S. Kwon

      Version of Record online: 1 JUL 2004 | DOI: 10.1002/adem.200405151

      Porous TiNi shape-memory alloy (TiNi SMA) bodies with controlled pore structure were produced from the (Ti+Ni) powder mixture by self-propagating high-temperature synthesis (SHS) An in vivo test was performed to evaluate bone tissue response and histocompatibility of porous TiNi SMA. No apparent adverse reactions such as inflammation and foreign body reaction were noted on or around all implanted porous TiNi SMA blocks. Bone ingrowth was found in the pore space of all implanted blocks.

    8. Gasar—A new Class of Porous Materials (pages 407–410)

      V. Shapovalov and L. Boyko

      Version of Record online: 1 JUL 2004 | DOI: 10.1002/adem.200405148

      The paper summarizes technology, structure, applications, and properties of gasars – new porous materials. The method consists of melting a material in a gas atmosphere to saturate it with hydrogen and directional solidifying under strictly controlled thermodynamic and kinetic conditions. The materials produced by this method, have a monolithic matrix and pores of proper geometric shapes, providing to gasars higher strength, plasticity, thermal and electrical conductivities as compared with those of other porous materials. Gasar is recommended for prospective application as filters, bearings, metal-matrix composites.

    9. Structure and Mechanical Properties of AFS Sandwiches Studied by in-situ Compression Tests in X-ray Microtomography (pages 411–415)

      L. Salvo, P. Belestin, E. Maire, M. Jacquesson, C. Vecchionacci, E. Boller, M. Bornert and P. Doumalin

      Version of Record online: 1 JUL 2004 | DOI: 10.1002/adem.200405152

      Al foam core/Al alloy skin sandwiches have potential for application in light weight structures. Recently, the foaming processes have improved and large, thick and 3D-shape panels can be produced using the precursor technology. The microstructure of an AFS sandwich is analysed in this paper at a microscale and a mesoscale using X-ray tomography and conventional SEM analysis. The main deformation mechanism of the core under compression is also studied thanks to in situ test.

    10. Real-time X-ray Radioscopy on Metallic Foams Using a Compact Micro-Focus Source (pages 416–420)

      F. García Moreno, M. Fromme and J. Banhart

      Version of Record online: 1 JUL 2004 | DOI: 10.1002/adem.200405143

      A measurement apparatus for observing the foaming of metals is described. The foaming of samples can be recorded in real-time with frequencies up to 9 Hz and resolutions down to 5 μm due to the small spot size. Magnifications up to 10× are obtained by simply changing the distance between source, sample and detector. Foaming of Al alloys and sandwiches was investigated and an image analysis program was developed to automatically recognise the foam expansion.

    11. The Role of Oxidation in Blowing Particle-Stabilised Aluminium Foams (pages 421–428)

      N. Babcsán, D. Leitlmeier, H.P. Degischer and J. Banhart

      Version of Record online: 1 JUL 2004 | DOI: 10.1002/adem.200405144

      Metal foams were produced by blowing gas into aluminium alloy melts and the effect of oxygen content of the blowing gas on composition and structure of the inner surface of the foam cells is studied. Scanning Electron Microscopy, Auger Electron Spectroscopy and Transmission Electron Microscopy are used to analyse the surfaces. Initially particle-free melts are pre-treated by bubbling air through them after which a certain degree of foam stability is achieved.

    12. Fracture of Metal Foams: In-situ Testing and Numerical Modeling (pages 429–431)

      P.R. Onck, R. van Merkerk, J.Th.M. De Hosson and I. Schmidt

      Version of Record online: 1 JUL 2004 | DOI: 10.1002/adem.200405156

      This paper is on a combined experimental/modeling study on the tensile fracture of open-cell foams. In-situ tensile tests show that individual struts can fail in a brittle or ductile mode, presumably depending on the presence of casting defects. In-situ single strut tests were performed, enabling observation of deformation and fracture behavior and, in addition, serving as calibration for the proposed single-strut model.

    13. Grain Size Effects on the Mechanical Behavior of Open-cell Nickel Foams (pages 432–439)

      V. Goussery, Y. Bienvenu, S. Forest, A.-F. Gourgues, C. Colin and J.-D. Bartout

      Version of Record online: 1 JUL 2004 | DOI: 10.1002/adem.200405153

      The dependence of the mechanical behavior of nickel foams upon their grain size was studied, as well as the grain size effects on the mechanical properties. The EBSD technique allowed observing the absence of preferred crystallographic orientations for both foams and foils. A mechanical model in the spirit of that by Gibson and Ashby was finally presented incorporating the grain size effect on yield strength and hardening modulus. This model provided a good estimation of the experimental data.

    14. The Collapse Response of Sandwich Beams with Aluminium Face Sheets and a Metal Foam Core (pages 440–443)

      V.L. Tagarielli, N.A. Fleck and V.S. Deshpande

      Version of Record online: 1 JUL 2004 | DOI: 10.1002/adem.200405154

      Plastic collapse modes of simply supported and clamped sandwich beams have been investigated experimentally and theoretically, for aluminium face sheets and Alporas foam core. The effect of clamped boundary conditions is to induce axial stretching after the initial yield mechanism. Hence, face sheet ductility dictates the level of energy absorption of the beam. Numerical and analytical predictions are validated by the available experimental evidence.

    15. Tensile Behaviour of Replicated Aluminium Foams (pages 444–447)

      J.-F. Despois, Y. Conde, C. San Marchi and A. Mortensen

      Version of Record online: 1 JUL 2004 | DOI: 10.1002/adem.200405155

      The replication process is used to produce open-cell 99.99 % pure aluminium foams of controlled pore diameter and solid volume fraction; each parameter is varied respectively from 40 to 400 μm and 10 to 30 vol. pct. The foam tensile behaviour is consistent with the small-strain compressive behaviour and shows a significant dependence on pore size.

    16. Aluminium Foam Sandwich (AFS) Ready for Market Introduction (pages 448–451)

      H.-W. Seeliger

      Version of Record online: 1 JUL 2004 | DOI: 10.1002/adem.200405140

      A novel production process for aluminium foam sandwich panels (AFS) is described. As an example for a serial application of AFS a support for a mobile telescope arm on a small lorry is presented and discussed.

    17. Process Stability in Serial Production of Aluminium Foam Panels and 3D Parts (pages 452–453)

      P. Schäffler and W. Rajner

      Version of Record online: 1 JUL 2004 | DOI: 10.1002/adem.200405141

      Powder Metallurgy (PM) technology is emerging as one of the most promising techniques for the manufacture of net shape components and panels of aluminium foam. Control of the stability of the aluminium foaming process is one of the key issues in a serial production. Since there are many different parameters to be controlled in the raw material, the precursor and the finished foam part, the best solution is to keep all these factors in one centre of competence to exclude external influences and transporting problems.

    18. CVD Technique for Inco Nickel Foam Production (pages 454–459)

      V. Paserin, S. Marcuson, J. Shu and D.S. Wilkinson

      Version of Record online: 1 JUL 2004 | DOI: 10.1002/adem.200405142

      In this paper, the capability of the CVD technique to produce uniform foams of different properties, with cell size ranging from ∼ 450 to ∼ 3200 μm, porosity from ∼ 70 to ∼ 98 %, and nominal thickness up to 3 mm is presented. In addition to the established application as a battery electrode material, some other potential capabilities and applications are explored.