Effect of precipitation on the development of dislocation substructure in low carbon steels during cold deformation

Abstract

Uniaxial tension tests were performed on titanium interstitial-free steels with varying titanium, carbon, and sulfur contents. For the same method of fabrication, variation of the composition creates a variation in the volume fraction of precipitates and/or in the content of titanium in solid solution. After 10% deformation, the observed dislocation microstructures are of cellular type, the cells being defined by primary walls of high dislocation density and secondary walls of a lower dislocation density which are more or less perpendicular to the primary walls. The spacing between primary walls is independent of the state of precipitation, and is comparable with values obtained in low carbon steels deformed under similar conditions. The average distance between secondary walls is dependent on the volume fraction of titanium carbide precipitates and is directly related to the average distance between particles in a plane. A simple type of Orowan formalism gives a satisfactory description of the type of interaction between precipitates and the dislocation microstructure. The following observations tend to confirm that room temperature may be considered as a transient temperature for low carbon steels.