Model for the Cottrell atmosphere formation during aging of ultra low carbon bake hardening steels

Abstract

A model describing the formation of the carbon atmosphere around a dislocation during aging of vacuum degassed ultra low carbon bake hardening steels has been developed by extending the original Cottrell theory taking into account the effects of the variation of the free carbon concentration, the saturation of dislocations and the segregation of carbon atoms to grain boundaries. Strain aging experiments have been carried out with an ultra low carbon steel and the experimental results been compared with the theoretical predictions. It is demonstrated that the model developed can describe the formation of Cottrell atmosphere in ultra low carbon bake hardening steels in industrial circumstances.