Advanced Engineering Materials

Cover image for Advanced Engineering Materials

November, 2003

Volume 5, Issue 11

Pages 761–823

    1. Polymer Nanocomposites for Aerospace Applications: Properties (pages 769–778)

      J. Njuguna and K. Pielichowski

      Version of Record online: 2 DEC 2003 | DOI: 10.1002/adem.200310101

      A wide variety of superior features qualifies polymer nanocomposites over the conventional carbon-fiber reinforced polymers for aerospace applications: increased modulus (see Figure for a demonstration of nanotube fiber flexibility), thermal and ablative performance, resistance to damage by atomic oxygen, to name just a few. In this review, both theoretical and experimental research on key properties (e.g., electrical, optical and mechanical) of the materials are discussed.

    2. Ultrasonic Torsion Welding of Sheet Metals to Cellular Metallic Materials (pages 779–786)

      C. Born, H. Kuckert, G. Wagner and D. Eifler

      Version of Record online: 4 DEC 2003 | DOI: 10.1002/adem.200310102

      Ultrasonic torsion welding joins metal foams to sheet metals with high performance: aluminum foam sandwich (AFS) and iron alloys may be joined before and after foaming (with tensile strengths of the weldings reaching up to 25 Mpa), and without significant deformation of the joining partners. An application example is given in the Figure which shows mechanical fasteners welded to pieces of non-foamed (left) and foamed AFS (right).

    3. Phase Stability of Nanoanatase (pages 787–788)

      H.M. Lu, W.X. Zhang and Q. Jiang

      Version of Record online: 2 DEC 2003 | DOI: 10.1002/adem.200300359

      A more precise determination of the critical particle size Dc for phase stability between nanocrystalline anatase and rutile is outlined by the authors. The predicted Dc value of 14 nm with a very weak temperature dependence between 550 and 850 °C (instead of an otherwise published Dc of 15 nm), which is deducted from theoretical calculations, is in agreement with thermodynamic measurements also presented.

    4. Wear Resistance of Multiphase Diffusion Carbide Coatings (pages 789–793)

      A. Młynarczak, K. Jozwiak and G. Mesmacque

      Version of Record online: 2 DEC 2003 | DOI: 10.1002/adem.200300395

      Diffusion carbide coatings of the types M7C3-VC and M7C3-TiC have been fabricated by pack cementation at 1000 °C on three tool steels. Coating hardness increases with FeV and FeTi concentration, while metallic luster increases with FeCr content. Wear behavior was found to be independent of the steel matrix; maximum wear resistance was achieved for M7C3-VC-TiC with Ti/V/Cr = 4/4/2. The Figure shows the shear of micro-roughness on one of the coatings.

    5. Dense Reaction Infiltrated Silicon/Silicon Carbide Ceramics Derived from Wood based Composites (pages 794–799)

      A. Hofenauer, O. Treusch, F. Tröger, G. Wegener, J. Fromm, M. Gahr, J. Schmidt and W. Krenkel

      Version of Record online: 4 DEC 2003 | DOI: 10.1002/adem.200300400

      Wood-based SiSiC ceramics with isotropic mechanical behavior were produced from commercial wood-based composites (e.g., fiber boards). Properties can be tuned by the compression of the starting material, and by the content of added phenolic resin, which influences pore density and the amount of SiC infiltrated. In turn, the abundance of SiC versus residual silicon and carbon in the product determines its mechanical strength.

    6. Continuous Liquid Phase Coating of Carbon Fibers with Kion VL 20® Polysilazane (pages 799–801)

      R. Gadow and F. Kern

      Version of Record online: 2 DEC 2003 | DOI: 10.1002/adem.200300394

      Carbon fiber coating with polymer preceramic precursors is an easy, inexpensive, and reproducible method of protecting carbon fibers against chemical and mechanical hazards (see Figure for a roving of HT carbon fibers coated with polysiloxane and calcined). Polysilazane Kion VL 20 was found to be superior to polysiloxanes because it makes coatings insensitive to drying and curing conditions; also, their tensile strength increases with coating thickness.

    7. Effect of Hypervelocity Impact on Microcellular Ceramic Foams from a Preceramic Polymer (pages 802–805)

      P. Colombo, A. Arcaro, A. Francesconi, D. Pavarin, D. Rondini and S. Debei

      Version of Record online: 2 DEC 2003 | DOI: 10.1002/adem.200300397

      A promising material for hypervelocity impact shields in spacecraft and satellites has been found in lightweight microcellular SiOC foams. The foam stops the projectile and the debris from the impacted bumper facesheet within a few millimeters (see Figure for a cross-section of the crater) at speeds up to 5.1 km s–1. The impacted SiOC ceramic did not react with incoming debris, and no phase transformation or compositional change was observed.

    8. Behavior of Stir-Cast Al-Alloy Particulate-Reinforced Metal-Matrix Composites under Successive Hot Rolling (pages 805–812)

      M.A. Taha, N.A. El-Mahallawy and A.M. El-Sabbagh

      Version of Record online: 2 DEC 2003 | DOI: 10.1002/adem.200300398

      A uniform particle distribution, plus less and smaller voids in strips of stir-cast particulate-reinforced metal matrix composites were attained using a successive hot rolling/ intermediate heating scheme, as demonstrated for Al 6063 alloy and SiC as reinforcement phase. Improved tensile strength and decrease of ductility were observed. The Figure visualizes the effect of the treatment on particle uniformity in transverse (top) and longitudinal sections (bottom).

    9. Selective Deposition of Hydroxyapatite Nanoparticles by Electrophoretic Deposition (pages 812–815)

      P. Mondragón-Cortez and G. Vargas-Gutiérrez

      Version of Record online: 2 DEC 2003 | DOI: 10.1002/adem.200300353

      Hydroxyapatite deposits with a polycrystalline, crack-free surface (see Figure for an SEM microimage) on stainless steel 316L substrates were obtained by a novel electrophoretic deposition (EPD) process. The procedure applies high voltage for very short times (0.5 to 1 s) thus avoiding structural agglomeration phenomena which prevail after 3 to 4 seconds under the same voltage. The dense packing of the nanoparticles affords very good sintering at 800 °C.

    10. Finite Element Simulation of an Industrial hot Rolling Schedule of Aluminium using Integrated Microstructure Models (pages 815–818)

      L. Neumann, H. Aretz, R. Kopp, M. Goerdeler and G. Gottstein

      Version of Record online: 2 DEC 2003 | DOI: 10.1002/adem.200300361

      The final properties of aluminum products largely depend on their temperature and forming history. To predict them, it is advantageous to combine process models and microstructural models. Here, the integration of a physically based dislocation density model with a full-constraints Taylor model into the FEM code Larstran/Shape is shown. Finally, the application of this modeling scheme to an industrial hot rolling schedule is demonstrated.

    11. Surface Tension, Phase Separation, and Solidification of Undercooled Cobalt–Copper Alloys (pages 819–823)

      I. Egry, D. Herlach, M. Kolbe, L. Ratke, S. Reutzel, C. Perrin and D. Chatain

      Version of Record online: 2 DEC 2003 | DOI: 10.1002/adem.200320508

      Liquid Cu–Co alloys can be undercooled below their liquidus temperature into the smetastable miscibility gap by using electromagnetic levitation, leading to phase separation into a cobalt-rich and a cobalt-poor phase. The Figure juxtaposes the shapes of two-phase drops with different sets of interfacial energies. Solidification experiments were performed in microgravity in order to minimize the effect of convection on the resulting microstructure.