Thermodynamic Modelling and Microstructural Study of Z-Phase Formation in a Ta-Alloyed Martensitic Steel

Florian Kerem Riedlsperger*, Bernadette Gsellmann, Erwin Povoden-Karadeniz, Oriana Tassa, Susanna Matera, Mária Dománková, Florian Kauffmann, Ernst Kozeschnik, Bernhard Sonderegger

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


A thermokinetic computational framework for precipitate transformation simulations in Ta-containing martensitic Z-steels was developed, including Calphad thermodynamics, diffusion mobility data from the literature, and a kinetic parameter setup that considered precipitation sites, interfacial energies and dislocation density evolution. The thermodynamics of Ta-containing subsystems were assessed by atomic solubility data and enthalpies from the literature as well as from the experimental dissolution temperature of Ta-based Z-phase CrTaN obtained from differential scanning calorimetry. Accompanied by a comprehensive transmission electron microscopy analysis of the microstructure, thermokinetic precipitation simulations with a wide-ranging and well-documented set of input parameters were carried out in MatCalc for one sample alloy. A special focus was placed on modelling the transformation of MX into the Z-phase, which was driven by Cr diffusion. The simulation results showed excellent agreement with experimental data in regard to size, number density and chemical composition of the precipitates, showing the usability of the developed thermokinetic simulation framework.
Original languageEnglish
Article number1332
Number of pages25
Issue number6
Publication statusPublished - 2 Mar 2021


  • thermodymics
  • precipitate kinetics
  • microstructure
  • modelling
  • steel
  • creep
  • Thermodynamics
  • Precipitate kinetics
  • Creep
  • Modelling
  • Microstructure
  • Steel

ASJC Scopus subject areas

  • Materials Science(all)

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