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

A model describing the formation of the carbon atmosphere around a dislocat ion during aging of vacuum degassed ultra low carbon bake hardening steels has been developed by extending the original Cottrell theory taking into ac count the effects of the variation of the free carbon concentration, the sa turation of dislocations and the segregation of carbon atoms to grain bound aries. Strain aging experiments have been carried out with an ultra low car bon steel and the experimental results been compared with the theoretical p redictions. It is demonstrated that the model developed can describe the fo rmation of Cottrell atmosphere in ultra low carbon bake hardening steels in industrial circumstances.