Beiträge zur Bewertung der Schwingfestigkeit von ausferritischem Gusseisen mit Kugelgraphit

Translated title of the contribution: Contributions to the Fatigue Behaviour of Austempered Ductile Iron

Manuel Wohlfahrt

Research output: ThesisDoctoral Thesis


An efficient design of casting components under the aspects of lightweight design and maximum utilisation of the material requires the application of innovative materials and the knowledge of mechanical properties and material models considering relevant influences on the material behaviour. The casting material, austempered ductile iron, is produced by an additional heat treatment of ferritic or pearlitic ductile iron, and is suitable for lightweight design due to the high flexibility of shape and its excellent strength and ductility. In the context of this work, relevant influences on static and cyclic material behaviour of austempered ductile iron have been investigated and the considerable increase of tensile strength and fatigue strength regarding to the base material was assessed. The results of tensile tests and microstructural analysis indicate the crucial influence of the heat treatment parameters, casting size, and content of alloying elements on the mechanical properties. If required, an adjustment of the heat treatment parameters or the amount of alloying elements is necessary to fulfil certain mechanical properties. To achieve proper mechanical properties a fully ausferritic microstructure is required. The fatigue strength of austempered ductile iron is significantly affected by the casting size and the presence of defects in the microstructure. This work provides material models to consider the influence of the technological size effect based on the solidification time or the formation of graphite nodules on fatigue strength and the assessment of variable defects sizes on local fatigue strength. The influence of mean stresses, notches, load type, and deep rolling on fatigue strength of austempered ductile iron have been investigated as well. These factors, in addition to the technological size effect, enable the design and the lifetime estimation of components based on the local stress approach.
Translated title of the contributionContributions to the Fatigue Behaviour of Austempered Ductile Iron
Original languageGerman
  • Grün, Florian, Assessor A (internal)
  • Bührig-Polaczek, Andreas, Assessor B (external)
Publication statusPublished - 2013

Bibliographical note

embargoed until null


  • Austempered Ductile Iron
  • ADI
  • technological size effect
  • heat treatment of cast iron
  • microshrinkage
  • casting surface
  • influences on fatigue strength

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