Influence of Deformation on the Precipitation Behavior of Nb(CN) in Austenite and Ferrite
- 564 Downloads
The evolution of Nb precipitates in a low-alloyed steel at 973 K (700 °C) as a function of strain and subsequent dwell time is studied via atom-probe tomography (APT) and transmission electron microscopy. The results show that the volume fraction of the precipitates increases with increasing accumulated deformation because deformation-induced dislocations act as nucleation sites. The chemistry of these precipitates which are Nb carbonitrides changes with the dwell time after the deformation step. With increasing time, the C fraction increases. The precipitation analysis by APT in the austenite and the ferrite reveals that precipitates in the ferrite are larger and exhibit a higher C fraction compared to the precipitates in the austenite after the same thermo-mechanical treatment. The investigations also show that the volume fraction of Nb carbonitrides in the ferrite is higher than in the austenite.
KeywordsFerrite Austenite Martensite Bainite Dwell Time
The financial support by the Austrian Federal Ministry of Economy, Family and Youth and the National Foundation for Research, Technology and Development is gratefully acknowledged.
- 1.T. Gladman: The Physical Metallurgy of Microalloyed Steels, The Institute of Materials, The University Press, London, 1997.Google Scholar
- 24.M.K. Miller, A. Cerezo, M.G. Hetherington, and G.D.W. Smith: Atom Probe Field Ion Microscopy, Oxford University Press Inc., Oxford, 1996, p. 532.Google Scholar
- 26.Thermodynamic database for Fe-systems, (mc_fe_v1.030.tdb), Institute of Materials Science and Technology, Vienna University of Technology, Austria.Google Scholar
- 27.Mobility database for Fe-systems, (mc_fe_v1.001.ddb), Institute of Materials Science and Technology, Vienna University of Technology, Austria.Google Scholar