Ferrite formation in a duplex stainless steel during controlled heating: X-ray diffraction and modeling using para-equilibrium diffusion kinetics

W. Zhang, Todd Palmer, J. W. Elmer, Tarasankar Debroy

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Abstract

The kinetics of the austenite to ferrite (γ→δ) transformation in a 2205 duplex stainless steel during controlled heating is examined using a combination of experimental and modeling techniques. The model of the γ→δ transformation is based on the assumption that this transformation is driven by the diffusion of nitrogen under para-equilibrium conditions. This one-dimensional diffusion model uses a moving grid method to track multiple moving interfaces and is capable of calculating the nitrogen diffusion across several grains during heating. The effect of different starting microstructures on the transformation kinetics is simulated by considering two y and two δ grains of varying sizes consistent with those in the base metal. The model predictions are compared with those measured experimentally using an in-situ x-ray diffraction technique. In this experimental technique, high energy synchrotron radiation is used to monitor the phases present in real-time under controlled heating conditions at 25 K/s. Comparison between calculations and experiments indicates that the model predicts δ fractions up to 30% higher than those observed experimentally at the beginning of the transformation. The difference between the calculated and measured δ fractions then starts to decrease, and the completion time predicted using the model agrees reasonably well with that measured. The possible cause of such discrepancy is discussed. Transformation kinetics from three different starting microstructures is calculated using the diffusion model and the effect of hard and soft impingements on the transformation kinetics is investigated.

Original languageEnglish (US)
Title of host publicationTrends in Welding Research - Proceedings of the 7th International Conference
Pages939-944
Number of pages6
Volume2005
StatePublished - Dec 1 2005
Event7th International Conference on Trends in Welding Research - Pine Mountain, GA, United States
Duration: May 16 2005May 20 2005

Other

Other7th International Conference on Trends in Welding Research
Country/TerritoryUnited States
CityPine Mountain, GA
Period5/16/055/20/05

All Science Journal Classification (ASJC) codes

  • Materials Science(all)
  • Mechanical Engineering

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