Advanced Engineering Materials

Cover image for Vol. 7 Issue 7

July, 2005

Volume 7, Issue 7

Pages 555–640

    1. Cover Picture: Thermal Conductivity Imaging of Thermal Barrier Coatings (Adv. Eng. Mater. 7/2005)

      X. Zheng, D. G. Cahill and J.-C. Zhao

      Version of Record online: 29 JUL 2005 | DOI: 10.1002/adem.200590013

      Thermal conductivity images of thermal barrier coatings are measured using time-domain thermoreflectance at a single delay time with micron-scale resolution. We find that the thermal conductivity of electron-beam physical vapor deposited 8 wt% yttria-stablized zirconia coatings for heat flow along both the through-thickness and in-plane directions is isotropic and uniform throughout the depth of the coating.

    2. Recent Progress in Corrosion and Protection of Magnesium Alloys (pages 563–586)

      G. Song

      Version of Record online: 29 JUL 2005 | DOI: 10.1002/adem.200500013

      Although corrosion performance is currently a severe problem with magnesium alloys, the prospect for magnesium alloys is promising because of their attractive advantages and potential applications. How to solve the corrosion problem has now become an important issue in the application of magnesium alloys. The aim of this overview is to deepen the current understanding of corrosion and protection of magnesium and its alloys and to provide a base for future research work in this field.

    3. Nanostructured Composite Materials with Improved Deformation Behavior (pages 587–596)

      J. Eckert, U. Kühn, J. Das, S. Scudino and N. Radtke

      Version of Record online: 29 JUL 2005 | DOI: 10.1002/adem.200400225

      A significant improvement of the room temperature ductility of fully nanocrystalline/glassy material can be achieved by developing a composite microstructure incorporating second phase precipitates with a different length scale in Zr-base multicomponent alloys. The formation of such a composite microstructure through simple casting techniques is described with the help of a metastable phase formation diagram.

    4. Nanoscale Energy Storage Materials Produced by Hydrogen-Driven Metallurgical Reactions (pages 597–601)

      J. Graetz and J. J. Reilly

      Version of Record online: 29 JUL 2005 | DOI: 10.1002/adem.200500028

      Nanoscale and nanocomposite lithium electrodes synthesized using hydrogen-driven metallurgical reactions demonstrate reversible lithium cycling at low temperature (298 °C). This novel synthesis technique may also be applied to the preparation of new, nanostructured, hydrogen storage compounds. These materials offer enhanced kinetics, material stability and gravimetric capacity, with respect to their bulk counterparts.

    5. Direct Evidence of a Deformation Mechanism Crossover in Nanocrystalline Nickel (pages 603–606)

      Z. Shan and S. X. Mao

      Version of Record online: 29 JUL 2005 | DOI: 10.1002/adem.200500034

      Evidence for deformation mechanism crossover, i.e. from dislocation nucleation and motion to grain boundary mediated plasticity, has been sought for many years, but direct experimental confirmation remains elusive. By employing in situ dynamics dark field transmission electron microscope investigation on nanocrystalline nickel films with an average grain size of about 10 nm, the authors show conclusive experimental evidence that grain boundary plasticity has begin to dominate the deformation of as deposited Ni. The physical mechanism that governs the observed phenomenon is discussed.

    6. Deformation Behavior of Free-Standing Pd-based Thin Film Metallic Glass for Micro Electro Mechanical Systems Applications (pages 606–609)

      G.-P. Zhang, Y. Liu and B. Zhang

      Version of Record online: 29 JUL 2005 | DOI: 10.1002/adem.200400187

      The deformation behavior of thin film metallic glasses (TFMG) both as-deposited and annealed at the supercooled liquid region (SCLR) near the Tg were investigated by bending TFMG microbeams. It was found that the shear banding behavior, the stress for operating the first shear band and the plastic shear displacement along the shear band plane were dependent on annealing time at the Tg. The deformation mechanism and the controlling of mechanical properties of the TFMG were discussed.

    7. HRTEM Study of Precipitates in Mg-Zn-Y Alloys as Cast and after Extrusion (pages 610–612)

      J. Rao, Y. Zhou, S. Yoshimoto, M. Yamasaki and Y. Kawamura

      Version of Record online: 29 JUL 2005 | DOI: 10.1002/adem.200500002

      Three kinds of precipitates were newly found, which are Mg3Zn3Y2, MgZn and MgZn2, in Mg-Zn-Y alloys both as-cast and after extrusion due to the composition concentration of Zn and Y on nanometer scale. This figure shows the high-resolution TEM image of MgZn precipitate in Mg substrate with the crystallographic parameters labeled in details. The boundary between MgZn precipitate and Mg substrate is very clear, no second phases were observed.

    8. The Potential of Powder Metallurgy for the Fabrication of Biomaterials on the Basis of Nickel-Titanium: A Case Study with a Staple Showing Shape Memory Behaviour (pages 613–619)

      L. Krone, J. Mentz, M. Bram, H.-P. Buchkremer, D. Stöver, M. Wagner, G. Eggeler, D. Christ, S. Reese, D. Bogdanski, M. Köller, S. A. Esenwein, G. Muhr, O. Prymak and M. Epple

      Version of Record online: 29 JUL 2005 | DOI: 10.1002/adem.200500029

      A staple from nickel-titanium shape memory alloy for foot surgery was prepared by metal injection moulding (powder metallurgy). After a thorough characterisation with a multitude of physical, chemical, mechanical, and biological methods, the prototype appears to be well suited for clinical use where a shape-memory effect is useful.

    9. Isolated Metal and Ceramic Micro Parts in the Sub-Millimeter Range Made by PIM (pages 619–622)

      S. Rath, L. Merz, K. Plewa, P. Holzer, T. Gietzelt and J. Hausselt

      Version of Record online: 29 JUL 2005 | DOI: 10.1002/adem.200500020

      The mass production of micro parts is an important step towards the fabrication of integrated micro systems in large scale. Powder injection molding allows to produce parts not only in high quantity but also with reduced or even without finishing. The presented results show that the production of micro parts even in the sub-millimeter range is possible with this process when specially designed feedstocks, an adapted tool concept and optimized post processing are used.

    10. Thermal Conductivity Imaging of Thermal Barrier Coatings (pages 622–626)

      X. Zheng, D. G. Cahill and J.-C. Zhao

      Version of Record online: 29 JUL 2005 | DOI: 10.1002/adem.200500024

      Thermal conductivity images of thermal barrier coatings are measured using time-domain thermoreflectance at a single delay time with micron-scale resolution. We find that the thermal conductivity of electron-beam physical vapor deposited 8 wt% yttria-stablized zirconia coatings for heat flow along both the through-thickness and in-plane directions is isotropic and uniform throughout the depth of the coating.

    11. The Effective Elastic Modulus of Laser-Engineered Composite Boride Coating (pages 626–629)

      T. Laha, A. Agarwal and N. B. Dahotre

      Version of Record online: 29 JUL 2005 | DOI: 10.1002/adem.200500032

      The effective elastic modulus of a laser-engineered composite TiB2 coating on AISI 1010 steel substrate has been computed using different micromechanics models and compared with the experimental values. The Hashin-Shtrikman Bound method evinced most consistent effective elastic modulus values compared to Eshelby and Mori-Tanaka models.

    12. Surface Modification of Pure Ti by Laser Alloying with B and Ni Mixed Powders (pages 629–632)

      Y. Tian, C. Chen, D. Wang and T. Lei

      Version of Record online: 29 JUL 2005 | DOI: 10.1002/adem.200400221

      Composite coatings were fabricated on the surface of pure titanium by laser alloying with B and Ni mixed powders. X-ray diffraction (XRD) spectrum shows that compounds such as TiB, TiB2 and NiTi are formed in the coatings. With surface microhardness of 1600–1700 HV0.1, the coatings have excellent wear resistance compared with the as received sample. The corrosion resistance of the annealed coatings is improved, but the unannealed coatings just have similar corrosion resistance as original pure titanium.

    13. Oxidation Damage of Spark Plug Electrodes (pages 633–640)

      J. Rager, A. Flaig, G. Schneider, T. Kaiser, F. Soldera and F. Mücklich

      Version of Record online: 29 JUL 2005 | DOI: 10.1002/adem.200500025

      Knowledge about the erosion mechanisms of spark plug materials is of fundamental interest for the development of materials with a high resistance against electrode erosion. Endurance tests were performed to study the wear behaviour of platinum, iridium, silver and nickel as electrode materials for spark plugs between 200 and 900 °C. Oxidation must be the dominating mechanism, irrespective of the material. Additional calculations resulted in the suggestion of a plasma-assisted oxidation process.

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