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R. Radis, E. Kozeschnik:
"The Precipitation Kinetics of Nb(C,N) in Plastically Deformed Microalloyed Steel";
Talk: Euromat 2011, Montpellier; 2011-09-12 - 2011-09-15.

The Precipitation Kinetics of Nb(C,N) in Plastically Deformed Microalloyed Steel
R. Radis1,2 and E. Kozeschnik1
1Christian Doppler Laboratory "Early Stages of Precipitation", Vienna University of Technology, Favoritenstraße 9-11, A-1040 Vienna, Austria
2Institute for Materials Science and Welding, Graz University of Technology, Kopernikusgasse 24, A-8010 Graz, Austria
The present work deals with the investigation of the influence of plastic deformation on the precipitation kinetics of Nb(C,N) in microalloyed steel. Using the thermo-kinetic software MatCalc, computer simulations of Nb(C,N) precipitation are carried out and compared to several independent experimental results, measured in the austenite as well as in the ferrite region of plastically deformed microalloyed steel. For this purpose, two separate populations of Nb(C,N) precipitates are used in the simulations, differing in the type of the nucleation sites, covering grain boundaries and dislocations. Furthermore, three different diffusion mechanisms are taken into account, which are the slow bulk diffusion in the matrix, enhanced diffusion along dislocation pipes as well as the fast short-circuit diffusion along grain boundaries. Apart from the dislocation density, which is varied according to different degrees of deformation, all simulations are performed with one set of input parameters. It is demonstrated, that deformations and/or quenching rates, introducing dislocation densities higher than 1013 m-2, lead to prominent diffusion along dislocation networks. Thus, in such cases, the precipitation kinetics of Nb(C,N) is dominated by the pipe diffusion mechanism and the precipitation process is several orders of magnitude faster compared to Nb(C,N) precipitation in undeformed, well annealed microalloyed steel.

precipitation kinetics