Solid state phase transformations in steels: a neutron and synchrotron radiation study

Haixing Fang

Research output: ThesisDissertation (TU Delft)

290 Downloads (Pure)


Solid-state phase transformations in steels cover a broad range of aspects. The underlying physics behind these phase transformations usually include nucleation, diffusion, lattice reconstruction and interactions between solutes and grain boundaries and interfaces. These features and the fact that the events take place at high temperatures, in the bulk, at time scales ranging from milliseconds to hours and at length scales ranging from atomic dimensions to millimeters make even the most widely studied phase transformation in steel, the austenite-ferrite phase transformation, only approximately understood and therefore an attractive topic for investigation. Quantitative data obtained by sophisticated physical characterization techniques in combination with supporting physical microstructural models addressing the relevant length and time scale are required to bring the field of ferrous physical metallurgy further.
This thesis focusses on two new approaches to orchestrate phase transformations in steels such that more physical insight is obtained or that new properties can be reached: (1) cyclic partial austenite-ferrite phase transformations that are designed to unravel the grain growth, and more specifically the interface mobility by avoiding concurrent nucleation of new phases. This topic is studied by computational studies and 3D neutron depolarization studies that are capable to in-situ monitor the ferrite grain size and fraction. (2) Self healing of creep damage by site selective precipitation of supersaturated iron-based alloys. A strong preference for precipitation at free creep cavity surfaces compared to that in the bulk can result in a filling of creep cavities and a significant extension of the creep life time. To make this self-healing mechanism applicable for creep-resistant steels, a search for an alternative healing agent for Au in Fe is to be executed and new design recipes need to be extracted on the basis of the experimental input from advanced characterization techniques such as electron microscopy and X-ray nanotomography.
Original languageEnglish
QualificationDoctor of Philosophy
Awarding Institution
  • Delft University of Technology
  • van Dijk, N.H., Supervisor
  • van der Zwaag, S., Supervisor
  • Brück, E.H., Supervisor
Award date10 Jan 2019
Print ISBNs978-94-028-1285-5
Publication statusPublished - 2019


  • Steels
  • Phase Transformations
  • Neutron scattering
  • Synchrotron radiation
  • Tomography
  • Self healing


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