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J. Six, A. Göksenli, S. Ilie, E. Kozeschnik:
"Investigation of the Hot Ductility Trough of Nb-Containing Low Alloy Steel";
Talk: Materials Science & Technology 2010, Houston, Texas, USA; 2010-10-17 - 2010-10-21; in: "Proceedings MS&T 2010", (2010), 10 pages.

It is well known that a fine dispersion of precipitates can strongly decrease the hot
ductility of low carbon steel at temperatures around 900 to 1000 °C. This is attributed to an
increase of the recrystallization start temperature during hot forming. In the present
investigation, focus is laid on the second ductility minimum and a correlation between the
measured fracture characteristics and NbC-precipitation observed in regions at and around the
austenite grain boundaries is attempted. In the analysis, several low carbon steel samples were
tensile tested to fracture at different temperatures. In order to quantify the size distribution of
the NbC precipitates at and around the grain boundaries, carbon extraction replica were
produced. The experimentally observed variation of ductility can be explained on the basis of
the differences in size and distribution of the NbC precipitates. The high density of small
precipitates at the lower test temperatures acts as an efficient inhibitor to recrystallization
during deformation and can clearly be made responsible for the significant decrease in hot
ductility in the second ductility trough.

second minimum of ductility, low alloy steel, NbC-precipitates