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M. Nöhrer, W. Mayer, S. Primig, S. Zamberger, E. Kozeschnik, H. Leitner:
"Influence of Deformation on the Precipitation Behavior of Nb(CN) in Austenite and Ferrite";
Metallurgical and Materials Transactions A - Physical Metallurgy and Materials Science, 45A (2014), Sept; 4210 - 4219.

The evolution of Nb precipitates in a low-alloyed steel at 973 K (700 A degrees 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.

http://dx.doi.org/10.1007/s11661-014-2373-3