Direct observation of niobium segregation to dislocations in steel.

It is well known that niobium in solute solution retards the recovery of dislocations in steel. Segregation of niobium atoms to dislocations was observed for the first time by atom probe tomography in niobium added ferritic stainless steels for high temperature use. The observation results suggest that solute niobium atoms solely have strong attractive interaction with dislocations. We name it niobium-Cottrell atmosphere, and discuss the trapping site and interaction energy through a comparison with segregation to the grain boundary in the same steel. [ABSTRACT FROM AUTHOR]