EFFECT OF PRECIPITATION ON THE DEVELOPMENT OF DISLOCATION SUBSTRUCTURE IN LOW-CARBON STEELS DURING COLD DEFORMATION

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