Advanced Engineering Materials

Cover image for Advanced Engineering Materials

June, 2003

Volume 5, Issue 6

Pages 385–453

    1. Contents: Adv. Eng. Mater. 6/2003 (pages 385–387)

      Version of Record online: 4 JUL 2003 | DOI: 10.1002/adem.200390032

    2. Titanium and Titanium Alloys—From Raw Material to Semi-finished Products (pages 393–398)

      H. Sibum

      Version of Record online: 4 JUL 2003 | DOI: 10.1002/adem.200310092

      Titanium still has the air of an exotic material despite being the fourth most abundant metal in the earth’s crust, and despite the broad use of its dioxide. The main reason for this paradox is the difficult and costly reduction of the oxide to the metal, which typically yields titanium as a sponge. In this review article, the way from this raw material to semi-finished titanium or Ti alloy parts (the Figure shows Ti-made heat exchanger plates) is outlined, a few applications presented and the recycling of the materials discussed.

    3. Continuous Fiber Reinforced Titanium Matrix Composites: Fabrication, Properties, and Applications (pages 399–410)

      C. Leyens, J. Hausmann and J. Kumpfert

      Version of Record online: 4 JUL 2003 | DOI: 10.1002/adem.200310093

      Titanium matrix composites (TMC’s) have been developed as high performance materials for light weight structural applications. They consist of a silicon carbide (SiC) fiber embedded in a titanium matrix, making use of both the high strength, stiffness, and creep resistance at elevated temperature of SiC and the damage tolerance of Ti alloys. Since materials properties depend on the quality of the fabrication process, TMC processing is important. The Figure shows the microstructure of a composite after consolidation and heat treatment.

    4. Titanium in Automotive Production (pages 411–418)

      O. Schauerte

      Version of Record online: 4 JUL 2003 | DOI: 10.1002/adem.200310094

      Although titanium has meanwhile made its way into serial production of automotive parts (see Figure for examples), its use has been limited to niche applications and was not driven by weighing the technical and economic aspects. Cost of semi-finished titanium products is still high; indeed, cheaper processes for production of Ti itself are urgently needed. However, if one extrapolates the current status of Ti technology from the historic development of the knowledge bases on the automotive metals steel, Al and Mg, the future of Ti use in cars looks quite bright.

    5. Titanium Alloys for Aerospace Applications (pages 419–427)

      M. Peters, J. Kumpfert, C.H. Ward and C. Leyens

      Version of Record online: 4 JUL 2003 | DOI: 10.1002/adem.200310095

      No other material is similarly suitable for aerospace use than titanium and its alloys. With a density of 4.5 g/cm3, Ti alloys are only about half as heavy as steel or Ni-based superalloys, and provide an excellent strength-to-weight ratio; furthermore, they exhibit exceptional corrosion resistance. In this review article, the use of titanium in the aerospace sector, including airframe, engine, helicopter, and space applications will be highlighted. As an example, the Figure shows the front fans of commercial Rolls-Royce Trent engines made of Ti-6Al-4V alloy.

    6. Thermal Cycling Setup for Testing Thermal Barrier Coatings (pages 429–432)

      F. Traeger, R. Vaßen, K.-H. Rauwald and D. Stöver

      Version of Record online: 4 JUL 2003 | DOI: 10.1002/adem.200300337

      Different mechanisms of failure can be induced and studied with the experimental setup for thermal-cycling tests developed by the authors and shown in the Figure. It offers a realistic test rig for a broad range of applications, being suitable for a large surface temperature range (1050–1400 °C) and thermal gradients of 0.4–1.0 K/μm through the ceramic layer. Cycle lengths are variable; typically, 5 min heating and 2 min cooling are chosen, since a steady state is normally reached after about 1 min of heating or cooling.

    7. Kinetics of Metallic Electrochemical Impregnation of Porous Anodic Oxidation Layer of 1050 and 2024 Aluminium Alloys (pages 433–435)

      L. Arurault and R.S. Bes

      Version of Record online: 4 JUL 2003 | DOI: 10.1002/adem.200300252

      Logarithmic growth kinetics with a rate law similar to the Elovich law account for metallic alternating-current electrochemical impregnation of the porous part of the anodised layer on aluminum alloys 1050A and 2024T3. The relation is based on the assumption that the rate of the limiting step decreases as a function of the amount of metal already deposited, which exerts a hindering effect on the reduction of aquatized metal cations; it is valid independent of the structure of the porous layer (columnar or spongy) and the deposited metal (Ni or Zn).

    8. Modeling of Environmental Degradation in Fatigue-Life Prediction of Near-α Titanium Alloy IMI 834 under Complex High-Temperature Loading Conditions (pages 435–440)

      R.G. Teteruk, H.-J. Christ and H.J. Maier

      Version of Record online: 4 JUL 2003 | DOI: 10.1002/adem.200300220

      The crack propagation model successfully applies to life-prediction of near-α-titanium alloy IMI 834 under complex high-temperature fatigue-loading conditions. The predictive capabilities of the model can be attributed to the close correlation of the model with the relevant damage mechanisms (among them environmental degradation under varying conditions) and micro-structural processes. The Figure shows an SEM image of a typical crack-initiation site for a test run at 400 °C.

    9. Investigations on the Machining of Sintered Titanium Foams Utilizing Face Milling and Peripheral Grinding (pages 441–447)

      M. Bram, C. Kempmann, A. Laptev, D. Stöver and K. Weinert

      Version of Record online: 4 JUL 2003 | DOI: 10.1002/adem.200300356

      Titanium foams are regarded as potent materials for biomedical applications such as bone implants, and are, if possible, manufactured close to their final shape by sintering processes. There are cases, however, in which it is necessary to generate the final shape by machining, and problems resulting from the porous structure and the material characteristics become critical. In this article, two important methods of machining, i.e. face milling and peripheral grinding, are investigated for their applicability to Ti foams, and their scope and limitations are discussed.

    10. Assessment of Microwave Heating for Sintering of Al/SiC and for in-situ Synthesis of TiC (pages 449–453)

      S. Leparoux, S. Vaucher and O. Beffort

      Version of Record online: 4 JUL 2003 | DOI: 10.1002/adem.200320136

      Microwave heating proves beneficial both for sintering of Al/SiC composites and for in-situ synthesis of TiC. In the Al/SiC case microwave energy is taken up by SiC grains, which leads to a sintering process that fails with conventional resistive heating. In Ti/C samples, the role of radiative energy is to heat up the material to 950 °C. There, reaction sintering sets in and titanium carbide is formed around the borders of the Ti particles, visible in a microphotograph as a light grey zone between Ti (white) and carbon (dark grey) particles (see Figure).