Kriechverhalten einer TiAl-Legierung für Anwendungen in Abgasturboladern

Translated title of the contribution: Creep behavior of a TiAl alloy for applications in exhaust turbochargers

Johann Kappacher

Research output: ThesisMaster's Thesis


Intermetallic titanium aluminides are likely to replace the about twice as heavy nickel-base alloys in exhaust gas turbocharger applications. The main advantages of this class of innovative high-temperature materials are their high specific yield strength and stiffness, good oxidation and burn resistance as well as their good creep resistance. In this study creep properties of a forged TNM alloy with a nominal composition of Ti-43.5Al-4Nb-1Mo-0.1B (at.%) and exhibiting a nearly-lamellar microstructure at the maximum load and temperature range of turbine wheels in diesel engines was investigated. On determination of stress exponent and activation energy, the steady-state strain rate could be described over a wide temperature and stress range. Through microstructural investigations of the as-forged material in scanning electron microscope (SEM) and transmission electron microscope (TEM), the effect of various microstructural constituents as amount of βo-phase or lamellar spacing on the creep behavior was discussed and correlated with the hardness of the material. Studies on the microstructural development after the creep tests by an SEM showed a stable microstructure up to the steady-state strain rate. By means of TEM images of selected creep specimen temperature-induced precipitations of βo phase in α2 lamellae could be reported for the first time in a TNM alloy. Finally, investigations of the microstructure of a turbine wheel examined in a hot-gas test facility showed good comparability with the reference material, but a slight deviation from the phase composition was determined. The gained data of this investigation provide a solid base that enables design optimised engineering of turbine wheels already in the planning and simulation stage.
Translated title of the contributionCreep behavior of a TiAl alloy for applications in exhaust turbochargers
Original languageGerman
  • Clemens, Helmut, Supervisor (internal)
Award date21 Oct 2016
Publication statusPublished - 2016

Bibliographical note

embargoed until 01-10-2021


  • intermetallic material
  • titanium aluminide
  • TiAl
  • creep
  • microstructural development
  • exhaust gas turbocharger
  • turbine wheel

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