Interaction of precipitation with austenite-to-ferrite phase transformation in vanadium micro-alloyed steels

Chrysoula Ioannidou (Corresponding author), Zaloa Arechabaleta, Alfonso Navarro-López, Arjan Rijkenberg, Robert M. Dalgliesh, Sebastian Kölling, Vitaliy Bliznuk, Catherine Pappas, Jilt Sietsma, Ad A. van Well, S. Erik Offerman

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Samenvatting

The precipitation kinetics of vanadium carbides and its interaction with the austenite-to-ferrite phase transformation is studied in two micro-alloyed steels that differ in vanadium and carbon concentrations by a factor of two, but have the same vanadium-to-carbon atomic ratio of 1:1. Dilatometry is used for heat-treating the specimens and studying the phase transformation kinetics during annealing at isothermal holding temperatures of 900, 750 and 650 °C for up to 10 h. Small-Angle Neutron Scattering (SANS) and Atom Probe Tomography (APT) measurements are performed to study the vanadium carbide precipitation kinetics. Vanadium carbide precipitation is not observed after annealing for 10 h at 900 and 750 °C, which is contrary to predictions from thermodynamic equilibrium calculations. Vanadium carbide precipitation is only observed during or after the austenite-to-ferrite phase transformation at 650 °C. The precipitate volume fraction and mean radius continuously increase as holding time increases, while the precipitate number density starts to decrease after 20 min, which corresponds to the time at which the austenite-to-ferrite phase transformation is finished. This indicates that nucleation and growth are dominant during the first 20 min, while later precipitate growth with soft impingement (overlapping diffusion fields) and coarsening take place. APT shows gradual changes in the precipitate chemical composition during annealing at 650 °C, which finally reaches a 1:1 atomic ratio of vanadium-to-carbon in the core of the precipitates after 10 h.

Originele taal-2Engels
Pagina's (van-tot)10-24
Aantal pagina's15
TijdschriftActa Materialia
Volume181
DOI's
StatusGepubliceerd - 1 dec 2019

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  • Citeer dit

    Ioannidou, C., Arechabaleta, Z., Navarro-López, A., Rijkenberg, A., Dalgliesh, R. M., Kölling, S., Bliznuk, V., Pappas, C., Sietsma, J., van Well, A. A., & Offerman, S. E. (2019). Interaction of precipitation with austenite-to-ferrite phase transformation in vanadium micro-alloyed steels. Acta Materialia, 181, 10-24. https://doi.org/10.1016/j.actamat.2019.09.046